In Wales, the UK Government is funding free period products to be accessed in schools, colleges, hospitals, and the premises of councils. [ 61 ] [ 62 ]


The Northern Ireland Executive is funding a scheme to put free period products in schools and colleges. [ 63 ]


In Northern Ireland, under the  Period Products (Free Provision) Act (Northern Ireland) 2022 , period products have been made accessible through the premises of public buildings. [ 64 ]


Period products are not exempt from GST, but are freely available at 14 locations on the island. [ 65 ]


Period products are exempt from GST, but there is no plan to freely provide period products at public places - the only schemes so far have been through charitable donations. [ 65 ] [ 66 ] [ 67 ]


Period products are exempt from GST. [ 65 ]


Currently, Tynwald bill is going to be introduced to make period products freely accessible. [ 68 ]


In the United States, there is no specialized tax on  tampons  or similar menstrual products. In states where  sales taxes  are collected, tampons and other menstrual products are taxed in much the same way as most other non-exempt items (such as toilet paper and toothpaste). There has been a recent push to carve out a special tax-exempt status for tampons and other menstrual products, and the tax on such items may be referred to as a type of pink tax called a " tampon tax ". [ 69 ]  As of 2020, 30 states collect sales tax from tampons. [ 70 ]  Women leading the movement against the tampon tax are calling the tax a form of "regulatory discrimination", saying that menstruation is out of their control and that the government should not tax something that is imminent for approximately half the population. [ 71 ]  Similarly, this puts an even greater strain onto poverty-stricken households and results in a large percentage of women and young girls being unable to afford them. For instance, in a 2015 Scotland study, it was discovered that "45% of girls" had used "toilet paper, socks and newspaper to replace menstrual products" because they were unable to afford them. [ 72 ]


Australia, Canada, and the United Kingdom have voted on legislation to create special tax exemptions for tampons, but none have become laws, [ 73 ]  until January 2019, when Australia made the decision to remove their tax on feminine products. [ 74 ]


Scotland  made period products free for all in 2020 [ 75 ]  and established a legal duty on local authorities to ensure that free items such as tampons and sanitary pads are available to "anyone who needs them". [ 76 ]  The rest of the UK followed suit in 2021. [ 77 ] [ 78 ]


The “Tampon Tax” refers to the sales tax imposed on menstrual hygiene products like mentioned previously. This additional tax further burdens women financially, which contributes to the wider issue of period poverty, where estimated one in four women and girls cannot afford menstrual products. Studies show that the pink tax or tampon tax on menstrual products can be as high as 13%. This disparity contributes to what is known as the tampon tax, where women are ending up having to pay thousands of dollars more over their lifetimes due to this discriminatory pricing practice. Efforts such as the “Tampon Tax Back” campaign seek to alleviate this burden by advocating for the elimination of the sales tax on all period products in various different states. However, despite progress in some areas, the Tampon tax remains a large barrier to menstrual health and financial equality for women.
 [ 79 ]


India has recently scrapped their tampon tax. [ 80 ]   Colombia  also abolished their tax on feminine hygiene products in November 2018 to help further push for gender equality. [ 74 ]  Germany's feminine products previously had a luxury tax, though at the start of 2020, they lowered the tax from 19% to the normal 7%. [ 74 ]


In November 2019, the largest sales tax protest took place against the 33 US states still implementing the tampon tax. [ 81 ]


In 2022 CVS dropped its taxes on women's hygiene products such as tampons and announced they will be covering the sales tax on these products in the U.S. states that allow them to do so. [ 82 ]


Recent developments in technology,  big data , and online consumerism research have found potential gender biased IT algorithms. [ 83 ]  A research study published in 2020 done at the University of Bamberg, Germany investigated gender specific differences in recommender systems in fashion. This study concluded that there were significant differences in price recommendations depending on which gender was being targeted, an online reflection of  gender-based price discrimination . [ 84 ]  Overall, product recommendations for women generally show a 5% higher premium compared to male counterparts. [ 84 ]  Further research is being pursued on digital gender-based price discrimination.


In recent news coming from the United States, New York state made into law the first prohibition on the pink tax, which went into effect in September 2020. Followed by California which has also introduced similar legislation. [ 85 ]


Opposition to the Pink Tax Repeal Act came from retailers and manufacturers of women's products and clothing. [ 50 ]  The main argument is that the Pink Tax Repeal Act would be difficult to enforce and lawsuits would follow. The difference between men's and women's products is not always easy to see, they argue, so removing the pink tax would be subjective. [ 86 ]  They also alleged that the bill was unfriendly to domestic manufacturing jobs and that lowering the prices for women's products could lead to employee layoffs. [ 50 ]


Republican  opposition for a recall of the tampon tax in Virginia argued that tax discrimination against products for women needed to be sorted out by changing the general tax code. They added that they supported the elimination of sales taxes overall. [ 35 ]


As a charity campaign for the political organization  EMILY's List  (a  political action committee  which supports the election of  Democratic  women who are  in favor of abortion rights ), the satirical card game  Cards Against Humanity  parodied the pink tax with a  "For Her" edition of its base set, which had pink packaging and was $5 more expensive. [ 87 ]


The consumer goods giant, Procter & Gamble, planned to take over the women's razor startup company Billie that provides women razors at a comparable price to men. However, the Federal Trade commission filed a complaint against the acquisition, claiming that it eliminates market competition. [ 88 ]


The  placental microbiome  is the  nonpathogenic ,  commensal   bacteria  claimed to be present in a healthy human  placenta  and is distinct from bacteria that cause infection and preterm birth in  chorioamnionitis . [ 1 ]  Until recently, the healthy placenta was considered to be a sterile organ but now  genera  and  species  have been identified that reside in the  basal layer . [ 2 ] [ 1 ]


It should be stressed that the evidence for a placental microbiome is controversial. [ 3 ] [ 4 ]  Most studies supporting the existence of a placental microbiome lack the appropriate experimental controls, and it has been found that contamination is most likely responsible for reports of a placental microbiome. [ 3 ] [ 5 ]


The placental microbiome more closely resembles that of the oral microbiome than either the vaginal or rectal microbiome. [ 1 ]


Culturable and non-culturable bacterial species in the placenta obtained following normal term pregnancy have been identified.


In a healthy placental microbiome, the diversity of the species and genera is extensive. [ 1 ]  A change in the composition of the microbiota in the placenta is associated with excess  gestational weight gain , and pre-term birth. [ 10 ]
The placental microbiota varies between low birth weight infants and those infants with normal birth weights. [ 13 ]
While bacteria are often found in the amniotic fluid of failed pregnancies, they are also found in particulate matter that is found in about 1% of healthy pregnancies. [ 9 ]


In non-human animals, part of the microbiome is passed onto offspring even before the offspring are born. Bacteriologists assume that the same probably holds true for humans. [ 9 ]


The fact that germ free animals can be routinely generated by sterile cesarean section provides strong experimental evidence for the sterile womb hypothesis.


Future research may find that the microbiota of the female reproductive tract may be related to  pregnancy , conception, and  birth . Animal studies have been used to investigate the relationship between oral microbiota and the placental microbiota. Mice inoculated with species of oral bacteria demonstrated placental colonization soon afterwards. [ 14 ]


Investigations into reproductive-associated microbiomes began around 1885 by Theodor Escherich. He wrote that  meconium  from the newborn was free of bacteria. This was interpreted as the uterine environment being sterile. Other investigations used sterile diapers for meconium collection. No bacteria were able to be cultured from the samples. Bacteria were detected and were directly proportional to the time between birth and the passage of meconium. A 1927 study demonstrated the presence of bacteria in the amniotic fluid of those that were in labor for longer than six hours. [ 15 ]


Sustainable menstruation  refers to the use of environmentally-friendly and responsible menstrual products. [ 1 ]


It is estimated that the average woman will bleed for an average of 40 years which can amount to upwards of 200 kg of menstrual product waste a year. To combat this environmental challenge, advocates of sustainable menstruation promote the use of reusable products such as  cloth menstrual pads ,  menstrual cups  and  period underwear , and also sustainably-produced biodegradable disposable products. [ 2 ]  Such practices reduce the waste created by disposable products (tampons and pads) made of non-biodegradable materials. [ 3 ] [ 4 ]


There is some concern that by focusing on menstruation as a focus in discussions in waste, it further  stigmatizes menstruation  by blaming women for problems they didn't create. In India, 6% of non-biodegradable waste is created by hygiene products including menstruation products, wipes and diapers. [ 5 ]


A  tampon  is a  menstrual  product designed to absorb blood and vaginal secretions by insertion into the  vagina  during  menstruation . Unlike a  pad , it is placed internally, inside of the  vaginal canal . [ 1 ]  Once inserted correctly, a tampon is held in place by the vagina and expands as it soaks up menstrual blood.


As tampons also absorb the vagina's natural lubrication and bacteria in addition to menstrual blood, they can increase the risk of  toxic shock syndrome  by changing the normal  pH  of the vagina and increasing the risk of  infections  from the bacterium  Staphylococcus aureus . [ 1 ] [ 2 ]  TSS is a rare but life-threatening infection that requires immediate medical attention. [ 3 ]


The majority of tampons sold are made of blends of  rayon  and  cotton , along with synthetic fibers. [ 4 ]  Some tampons are made out of organic cotton. Tampons are available in several absorbency ratings.


Several countries regulate tampons as medical devices. In the United States, they are considered to be a Class II medical device by the  Food and Drug Administration  (FDA). [ 5 ]  They are sometimes used for  hemostasis  in  surgery .


Tampon design varies between companies and across product lines in order to offer a variety of applicators, materials and absorbencies. [ 6 ]  There are two main categories of tampons based on the way of insertion – digital tampons inserted by finger, and applicator tampons. Tampon applicators may be made of plastic or cardboard, and are similar in design to a syringe. The applicator consists of two tubes, an "outer", or barrel, and "inner", or plunger. The outer tube has a smooth surface to aid insertion and sometimes comes with a rounded end that is petaled. [ 7 ] [ 8 ]


Differences exist in the way tampons expand when in use: applicator tampons generally expand axially (increase in length), while digital tampons will expand radially (increase in diameter). [ 9 ]  Most tampons have a cord or string for removal. The majority of tampons sold are made of rayon, or a blend of  rayon  and  cotton . Organic cotton tampons are marketed as 100% cotton, but they may have plastic covering the cotton core. [ 10 ]  Tampons may also come in scented or unscented varieties. [ 7 ]


Tampons are available in several absorbency ratings, which are consistent across manufacturers in the U.S. These differ in the amount of cotton in each product and are measured based on the amount of fluid they are able to absorb. [ 11 ]  The absorbency rates required by the  U.S. Food and Drug Administration  (FDA) for manufacturer labeling are listed below: [ 12 ]


Absorbency ratings outside the US may be different. The majority of non-US manufacturers use absorbency rating and Code of Practice [ 13 ]  recommended by  EDANA  (European Disposables and Nonwovens Association).


In the UK, the Absorbent Hygiene Product Manufacturers Association (AHPMA) has written a Tampon Code of Practice which companies can follow on a volunteer basis. [ 14 ]  According to this code, UK manufacturers should follow the (European) EDANA code (see above).


A piece of test equipment referred to as a Syngyna (short for synthetic vagina) is usually used to test absorbency. The machine uses a  condom  into which the tampon is inserted, and synthetic menstrual fluid is fed into the test chamber. [ 15 ]


A novel way of testing was developed by feminist medical experts after the  toxic shock syndrome  (TSS) crisis, and used blood – rather than the industry standard blue saline – as a test material. [ 16 ]


The  FDA  requires the manufacturer to perform absorbency testing to determine the absorbency rating using the Syngyna method or other methods that are approved by the FDA. The manufacturer is also required to include on the package label the absorbency rating and a comparison to other absorbency ratings as an attempt to help consumers choose the right product and avoid complications of TSS. In addition, The following statement of association between tampons and TSS is required by the FDA to be on the package label as part of the labeling requirements: "Attention: Tampons are associated with Toxic Shock Syndrome (TSS). TSS is a rare but serious disease that may cause death. Read and save the enclosed information." [ 12 ]


Such guidelines for package labeling are more lenient when it comes to tampons bought from vending machines. For example, tampons sold in vending machines are not required by the FDA to include labeling such as absorbency ratings or information about TSS. [ 12 ]


The average person who menstruates uses approximately 11,400 tampons in their lifetime, assuming exclusive use of tampons. Tampon prices have risen due to inflation and supply chain challenges. Currently, a box of tampons typically costs between $7 and $12 USD and contains 16 to 40 tampons, depending on the brand and size. This means users might spend between $63 and $108 annually on tampons alone, assuming the need for around 9 boxes per year. This corresponds to an average cost of approximately $0.22–$0.75 per tampon, reflecting price increases of up to 33% since the pandemic. [ 17 ] [ 18 ]
Activists call the problem some women have when not being able to afford menstrual products " period poverty ". The fact that, in certain U.S. states, sales tax applies to menstrual products is referred to as a "tampon tax". As of 2024, 23 states exempt these products, while others impose taxes up to 7%. Local taxes can also apply, adding further costs. Some states such as Texas recently abolished this tax. Some states provide free tampons and pads in public schools and prisons, helping to alleviate period poverty. [ 19 ] [ 20 ]


Menstrual toxic shock syndrome (mTSS) is a life-threatening disease most commonly caused by infection of  superantigen -producing  Staphylococcus aureus . The superantigen toxin secreted in  S. aureus  infections is TSS Toxin-1, or  TSST -1. Incidence ranges from 0.03 to 0.50 cases per 100,000 people, with an overall mortality around 8%. [ 21 ]  mTSS signs and symptoms include fever (greater than or equal to 38.9 °C), rash,  desquamation ,  hypotension  ( systolic blood pressure  less than 90 mmHg), and multi-system organ involvement with at least three systems, such as gastrointestinal complications (vomiting),  central nervous system  (CNS) effects (disorientation), and  myalgia . [ 22 ]


Toxic shock syndrome was named by James K. Todd in 1978. [ 23 ]  Philip M. Tierno Jr., Director of Clinical  Microbiology  and  Immunology  at the  NYU Langone Medical Center , helped determine that tampons were behind  toxic shock syndrome  (TSS) cases in the early 1980s. Tierno blames the introduction of higher-absorbency tampons made with rayon in 1978, as well as the relatively recent decision by manufacturers to recommend that tampons can be worn overnight, for the surge in cases of TSS. [ 24 ]  However, a later  meta-analysis  found that the material composition of tampons is not directly correlated to the incidence of toxic shock syndrome, whereas  oxygen  and  carbon dioxide  content of menstrual fluid uptake is associated more strongly. [ 25 ] [ 26 ] [ 27 ]


In 1982, a liability case called  Kehm v. Proctor & Gamble  took place, where the family of Patricia Kehm sued  Procter & Gamble  for her death on September 6, 1982, from TSS, while using  Rely brand tampons . The case was the first successful case to sue the company. Procter & Gamble paid $300,000 in compensatory damages to the Kehm family. This case can be attributed to the increase in regulations and safety protocol testing for current FDA requirements. [ 2 ]


Some risk factors identified for developing TSS include recent  labor and delivery , tampon use, recent staphylococcus infection, recent  surgery , and foreign objects inside the body. [ 28 ]


The FDA suggests the following guidelines for decreasing the risk of contracting TSS when using tampons: [ 29 ] [ 30 ]


The FDA also advises those with a history of TSS not to use tampons and instead turn to other  feminine hygiene  products to control menstrual flow. [ 31 ]  Other menstrual hygiene products available include pads,  menstrual cups , menstrual discs, and reusable period underwear. [ 1 ]


Cases of tampon-connected TSS are very rare in the United Kingdom [ 32 ] [ 33 ] [ 34 ]  and United States. [ 35 ] [ 36 ]  A controversial study by Tierno found that all-cotton tampons were less likely than rayon tampons to produce the conditions in which TSS can grow. [ 37 ]  This was done using a direct comparison of 20 brands of tampons, including conventional cotton/rayon tampons and 100% organic cotton tampons. [ 38 ]  In a series of studies conducted after this initial claim, it was shown that all tampons (regardless of composition) are similar in their effect on TSS and that tampons made with rayon do not have an increased incidence of TSS. [ 21 ]  Instead, tampons should be selected based on minimum absorbency rating necessary to absorb flow corresponding to the individual. [ 30 ]


Sea sponges  are also marketed as  menstrual  hygiene products. A 1980 study by the  University of Iowa  found that commercially sold sea sponges contained harmful materials like  sand  and  bacteria . [ 39 ]


Studies have shown non-significantly higher mean levels of mercury in tampon users compared to non tampon users. No evidence showed an association between tampon use and inflammation biomarkers. [ 40 ]


According to the Women's Environmental Network research briefing on menstrual products made from wood pulp: [ 41 ]


The basic ingredient for menstrual pads is wood pulp, which begins life as a brown coloured product. Various 'purification' processes can be used to bleach it white. Measurable levels of dioxin have been found near paper pulping mills, where chlorine has been used to bleach the wood pulp. Dioxin is one of the most persistent and toxic chemicals, and can cause reproductive disorders, damage to the immune system and cancer (26). There are no safe levels and it builds up in our fat tissue and in our environment.


In the UK, the Marine Conservation Society has researched the prevalence and problem of plastic tampon applicators found on beaches. [ 42 ]


Disposal of tampons, especially flushing (which manufacturers warn against) may lead to clogged drains and waste management problems. [ 43 ]


There are multiple cases in which the use of tampons may need medical advice from a healthcare professional. For example, as part of the  National Institutes of Health , the  U.S. National Library of Medicine  and its branch  MedlinePlus  advise against using tampons while being treated with any of several medications taken by the vaginal route such as vaginal suppositories and creams, as tampons may decrease the absorbance of these drugs by the body. Example of these medications include  clindamycin , [ 44 ]   terconazole , [ 45 ]   miconazole , [ 46 ]   clotrimazole , [ 47 ]  when used as a vaginal cream or vaginal suppository, as well as  butoconazole  vaginal cream. [ 48 ]


According to the American Society for Blood and Marrow Transplantation (ASBMT), tampons may be responsible for an increased risk of infection due to the erosions it causes in the tissue of the cervix and vagina, leaving the skin prone to infections. Thus, ASBMT advises  hematopoietic stem cell transplantation  recipients against using tampons while undergoing therapy. [ 49 ]


Tampons are currently being used and tested to restore and/or maintain the normal microbiota of the vagina to treat  bacterial vaginosis . [ 50 ]   Some of these are available to the public but come with disclaimers. [ 51 ]  The efficacy of the use of these  probiotic  tampons has not been established.


Tampons have also been used in cases of tooth extraction to reduce post-extraction bleeding. [ 52 ]


Tampons are currently being investigated as a possible use to detect  endometrial cancer . [ 53 ]  Endometrial cancer does not currently have effective  cancer screening  methods if an individual is not showing symptoms. [ 54 ]  Tampons not only absorb menstrual blood, but also vaginal fluids. The vaginal fluids absorbed in the tampons would also contain the cancerous DNA, and possibly contain precancerous material, allowing for earlier detection of endometrial cancer. [ 55 ]   Clinical trials are currently being conducted to evaluate the use of tampons as a screening method for early detection of endometrial cancer.


Appropriate disposal of used tampons is still lacking in many countries. Because the lack of menstrual management practices in some countries, many sanitary pads or other menstrual products will be disposed into domestic solid wastes or garbage bins that eventually becomes part of a solid wastes. [ 56 ]


The issue that underlies the governance or implementation of menstrual waste management is how country categorizes menstrual waste. This waste could be considered as a common household waste, hazardous household waste (which will required to be segregated from routine household waste), biomedical waste given amount of blood it contains, or  plastic waste  given the plastic content in many commercial disposal pads (some only the outer case of the tampon or pads). [ 57 ]


Ecological impact varies according to disposal method (whether a tampon is flushed down the toilet or placed in a garbage bin – the latter is the recommended option). Factors such as tampon composition will likewise impact  sewage treatment plants  or waste processing. [ 58 ]  The average use of tampons in menstruation may add up to approximately 11,400 tampons in someone's lifetime (if they use only tampons rather than other products). [ 59 ]  Tampons are made of cotton, rayon, polyester, polyethylene, polypropylene, and fiber finishes. Aside from the cotton, rayon and fiber finishes, these materials are not  biodegradable . Organic cotton tampons are biodegradable, but must be composted to ensure they break down in a reasonable amount of time. Rayon was found to be more biodegradable than cotton. [ 60 ]


Environmentally friendly alternatives to using tampons are the  menstrual cup ,  reusable sanitary pads ,  menstrual sponges , reusable tampons, [ 61 ]  and  reusable absorbent underwear . [ 62 ] [ 63 ] [ 64 ]


The Royal Institute of Technology in Stockholm carried out a  life-cycle assessment  (LCA) comparison of the environmental impact of tampons and sanitary pads. They found that the main environmental impact of the products was in fact caused by the processing of raw materials, particularly  LDPE  (low density polyethylene) – or the plastics used in the backing of pads and tampon applicators, and  cellulose production . As production of these plastics requires a lot of energy and creates long-lasting waste, the main impact from the life cycle of these products is  fossil fuel  use, though the waste produced is significant in its own right. [ 65 ]


The menstrual material was disposed according to the type of product, and even based on cultural beliefs. This was done regardless of giving any importance to the location and proper techniques of disposal. In some areas of the world, menstrual waste is disposed into pit latrines, as burning and burial were difficult due to limited private space. [ 56 ]


Women have used tampons during menstruation for thousands of years. In her book  Everything You Must Know About Tampons  (1981), Nancy Friedman writes, [ 66 ]


[T]here is evidence of tampon use throughout history in a multitude of cultures. The oldest printed medical document,  Ebers Papyrus , refers to the use of soft papyrus tampons by Egyptian women in the fifteenth century B.C. Roman women used wool tampons. Women in ancient Japan fashioned tampons out of paper, held them in place with a bandage, and changed them 10 to 12 times a day. Traditional Hawaiian women used the furry part of a native fern called  hapu'u ; and grasses, mosses and other plants are still used by women in parts of Asia and Africa.


R. G. Mayne defined a tampon in 1860 as: "a less inelegant term for the  plug , whether made up of portions of rag, sponge, or a silk handkerchief, where plugging the  vagina  is had recourse to in cases of hemorrhage." [ 67 ]


Earle Haas  patented the first modern tampon,  Tampax , with the tube-within-a-tube applicator. Gertrude Schulte Tenderich (née Voss) bought the patent rights to her company trademark Tampax and started as a seller, manufacturer, and spokesperson in 1933. [ 68 ]  Tenderich hired women to manufacture the item and then hired two sales associates to market the product to drugstores in Colorado and Wyoming, and nurses to give public lectures on the benefits of the creation, and was also instrumental in inducing newspapers to run advertisements.


In 1945, Tampax presented a number of studies to prove the safety of tampons. A 1965 study by the Rock Reproductive Clinic stated that the use of tampons "has no physiological or clinical undesired side effects". [ 23 ]


During her study of female anatomy, German gynecologist  Judith Esser-Mittag  developed a digital-style tampon, which was made to be inserted without an applicator. In the late 1940s, Carl Hahn and Heinz Mittag worked on the mass production of this tampon. Hahn sold his company to  Johnson & Johnson  in 1974. [ 69 ]


In 1992, Congress found an internal FDA memo about the presence of  dioxin , a known carcinogen, in tampons. [ 70 ]  Dioxin is one of the toxic chemicals produced when wood pulp is bleached with chlorine. [ 71 ]  Congressional hearings were held and tampon manufacturers assured Congress that the trace levels of dioxin in tampons was well below EPA level. The EPA has stated there is no acceptable level of dioxin. [ 70 ]  Following this, major commercial tampon brands began switching from dioxin-producing chlorine gas bleaching methods to either elemental "chlorine-free" or "totally chlorine free" bleaching processes. [ 72 ]


In the United States, the Tampon Safety and Research Act was introduced to Congress in 1997 in an attempt to create transparency between tampon manufacturers and consumers. The bill would mandate the conduct or support of research on the extent to which additives in feminine hygiene products pose any risks to the health of women or to the children of women who use those products during or before the pregnancies involved. [ 73 ]  Although yet to be passed, the bill has been continually reintroduced, most recently in 2019 as the  Robin Danielson Feminine Hygiene Product Safety Act . [ 74 ]  Data would also be required from manufacturers regarding the presence of dioxins, synthetic fibers, chlorine, and other components (including contaminants and substances used as fragrances, colorants, dyes, and preservatives) in their feminine hygiene products.


"Tampon tax" refers to tampons' lack of tax exempt status that is often in place for other basic need products.  Several political statements have been made in regards to tampon use. In 2000, a 10%  goods and services tax  (GST) was introduced in Australia. While lubricant, condoms, incontinence pads and numerous medical items were regarded as essential and exempt from the tax, tampons continue to be charged GST. Prior to the introduction of GST, several states also applied a  luxury tax  to tampons at a higher rate than GST. Specific petitions such as "Axe the Tampon Tax" have been created to oppose this tax, and the tax was removed in 2019. [ 75 ]
In the  UK , tampons are subject to a zero rate of  value added tax  (VAT), as opposed to the standard rate of 20% applied to the vast majority of products sold in the country. [ 76 ]  The UK was previously bound by the EU VAT directive, which required a minimum of 5% VAT on sanitary products. Since 1 January 2021, VAT applied to menstrual sanitary products has been 0%.


In Canada, the federal government has removed the  goods and services tax  (GST) and  harmonized sales tax  (HST) from tampons and other menstrual hygiene products as of 1 July 2015. [ 77 ]


In the US, access to menstrual products such as pads and tampons and taxes added on these products, have also been controversial topics especially when it comes to people with low income. [ 78 ]  Laws for exempting such taxes differ vastly from state to state. [ 78 ]  The  American Civil Liberties Union  (ACLU) has published a report discussing these laws and listing the different guidelines followed by institutions such as schools, shelters, and prisons when providing menstrual goods. [ 78 ]


The report by ACLU also discusses the case of Kimberly Haven who was a former prisoner that had a  hysterectomy  after she had experienced  toxic shock syndrome  (TSS) due to using handmade tampons from toilet paper in prison. [ 79 ] [ 78 ]  Her testimony supported a Maryland bill that is intended to increase access of menstrual products for imprisoned women. [ 78 ]


Historically, the word "tampon" originated from the medieval  French  word " tampion ", meaning a piece of cloth to stop a hole, a  stamp ,  plug , or  stopper . [ 80 ]


There is a misconception described as sexist [ 81 ] [ 82 ]  that using a tampon rids a person of their  virginity . This is because some cultures regard virginity as indicated by whether the  hymen  is still intact, and may believe that inserting a tampon breaks the hymen. However, this belief is not rooted in medical science. The hymen, a thin membrane partially covering the vaginal opening, varies greatly in thickness, elasticity, and shape from person to person. It almost never blocks the entire vaginal opening, stretches and thins naturally over time, and can stretch or break due to non-sexual everyday activities such as exercise; [ 83 ] [ 84 ]  conversely, it may not break even after penetrative sexual intercourse, as it is able to stretch. [ 85 ]  Therefore, the presence or condition of the hymen is not an indicator of virginity.


Medical professionals have pointed out that misconceptions about the hymen lead to medically unfounded and harmful practices such as  virginity testing  and  hymenoplasty . [ 86 ]


In  Stephen King's  novel  Carrie , the title character is bullied for menstruating and is bombarded with tampons and pads by her peers.


In 1985, Tampon Applicator Creative Klubs International (TACKI) was established to develop creative uses for discarded, non-biodegradable, plastic feminine hygiene products, commonly referred to as "beach whistles". TACKI President Jay Critchley launched his corporation in order to develop a global folk art movement and cottage industry, promote awareness of these throwaway objects washed up on beaches worldwide from faulty sewage systems, create the world's largest collection of discarded plastic tampon applicators, and ban their manufacture and sale through legislative action. The project and artwork was carried out during numerous site-specific performances and installations. [ 87 ]


Tampons are traditionally marketed as products for women, conserving the idea that menstruation only affects  cisgender  women, or women who were assigned female at birth and continue to identify with that label. This framing marginalizes  transgender  men,  nonbinary  individuals, and genderqueer people who menstruate. This makes their experiences with menstruation largely invisible in public discourse, marketing, and product design. Addressing gender inclusion in the context of tampons involves examining societal stigmas, access challenges, and evolving efforts to create more inclusive spaces for all people who menstruate. In recent years, when discussing periods, academia has shifted terminology to be more inclusive, thus beginning to use the term "menstruators" instead of "women." [ 88 ]


Additionally, public restrooms often reinforce a binary understanding of  gender . Men’s restrooms rarely, if ever, provide menstrual product dispensers, leaving many queer people without access to tampons when needed. [ 89 ]  When using the women's bathroom in attempt to have access to period products, transgender and nonbinary individuals may face safety concerns or harassment for accessing restrooms that align with their gender identity.


Some menstrual product companies, such as Aunt Flow and Thinx, have started using inclusive language like “menstrual products” instead of “feminine hygiene products.” These efforts aim to normalize menstruation for all individuals who experience it, regardless of gender. In marketing, efforts to redesign tampon packaging to be more gender-neutral help make these products less alienating for trans and nonbinary users.  [ 90 ]  Removing pink or floral designs, for example, makes them more approachable.


Access to tampons is shaped by significant socioeconomic disparities, with systemic barriers disproportionately affecting individuals from low-income backgrounds. These disparities show up in various ways, including affordability challenges, stigmatization, and inadequate infrastructure. [ 91 ]  Addressing these issues requires recognizing how economic inequality intersects with social factors to restrict access to menstrual products like tampons.


A large issue in our society is  period poverty , which refers to the lack of access to menstrual products, hygiene facilities, and education due to financial constraints. It is a prevalent issue in both developing and developed countries, where many people cannot afford tampons and other menstrual products. In many low-income communities, individuals often miss school, work, or social activities due to a lack of menstrual products. This contributes to cycles of poverty, as menstruation becomes a barrier to education and economic opportunities. [ 92 ]  Globally, an estimated 500 million people face period poverty. In United States, studies have shown that one in five students have struggled to afford menstrual products. [ 93 ]


Many schools, shelters, and prisons fail to provide tampons for free or in sufficient quantities. [ 94 ]  Low-income students, in particular, may resort to unsafe alternatives like paper towels or rags, which can lead to health risks such as infections. Homeless menstruators face unique challenges, as they often lack both the financial means to purchase tampons and access to clean facilities for changing them. [ 95 ]  Nonprofits like The Homeless Period Project work to distribute tampons to these populations, but systemic support is still lacking.


Racial inequities in access to menstrual products are shaped by a complex interplay of systemic racism, socioeconomic disparities, cultural stigmas, and  healthcare inequality . These inequities disproportionately affect menstruators from marginalized backgrounds, limiting their access to essential products.


Menstruators from racialized communities are more likely to live in poverty due to historical economic inequities. This economic disadvantage makes purchasing tampons and other menstrual products a financial burden. [ 96 ]  This is because in some predominantly Black and Brown communities, menstrual products may be sold at higher prices due to fewer retail options and the " poverty tax ," where essential goods cost more in underserved areas.


Cultural stigmas around menstruation can be particularly pronounced in certain racial and ethnic communities, where periods may be considered taboo or inappropriate to discuss openly. [ 97 ]  This silence can discourage menstruators from seeking tampons or advocating for their needs. In some cultures, tampons are viewed with suspicion. They are linked to myths about virginity or seen as inappropriate for younger menstruators. These beliefs can limit the willingness or ability of individuals in certain racial groups to access tampons.


Additionally, schools in marginalized racial communities often lack comprehensive menstrual education programs. This lack of education can leave menstruators unaware of the variety of menstrual products available, or unsure how to use them safely. On top of that, racial biases in the education system may contribute to a lack of attention to the menstrual health needs of students from different racial groups. [ 98 ]


There are many other aspects of racial inequity when it comes to menstrual product education and accessibility. People of color are less likely to have access to adequate  gynecological  care, and more likely to face discrimination in the health world regardless of their health issue. To add onto that, the diverse needs of people from ethnic backgrounds have historically been neglected by marketing companies. [ 99 ]  When advertising does attempt to include people of color, it often fails to address the unique cultural stigmas, challenges, or values that shape their experiences with menstruation.


Individuals with conditions that affect fine motor skills or hand strength (e.g.,  arthritis ,  cerebral palsy , or  multiple sclerosis ) may find it difficult to unwrap, insert, or remove tampons. [ 100 ]  The small size of tampons and their applicators can be a significant barrier. Most tampons are designed with the assumption of able-bodied users, lacking features like  ergonomic  grips, adaptive applicators, or designs that accommodate reduced hand mobility.  Public restrooms, especially those not compliant with accessibility standards, may not provide sufficient space or the necessary support structures (e.g., grab bars) for disabled individuals to manage tampon insertion or removal. People who struggle with vision may encounter difficulties identifying tampon sizes, brands, or instructions due to the lack of  braille  on packaging or tactile features on the products themselves. For menstruators with hearing impairments, they may miss out on important product usage information if it is only provided through audio formats or poorly captioned content.


People with  intellectual  or  developmental disabilities  may require additional support to learn how to use tampons safely and effectively. Complex instructions, such as proper insertion angles and removal timing, can be challenging to navigate without guidance. Caregivers or support workers may need to assist disabled menstruators with tampon usage. However, this raises concerns about autonomy, privacy, and dignity, as menstruation is a deeply personal experience.


Certain disabilities or  chronic illnesses  (e.g.,  endometriosis ,  pelvic floor disorders , or  interstitial cystitis ) may make tampon use uncomfortable or painful. These conditions can limit access to tampons as a viable option for menstrual care. Some disabled individuals have heightened sensitivity to tampon materials (e.g.,  rayon ,  chlorine bleach , or  fragrances ), which can increase discomfort or lead to allergic reactions.


Disabled menstruators often face compounded stigma, as society tends to marginalize both disabled individuals and discussions around menstruation. [ 101 ]  This can lead to isolation and discomfort in seeking out appropriate menstrual products.


Advocacy around tampons intersects with broader movements for menstrual equity. These movements aim to dismantle the societal, economic, and cultural barriers that perpetuate inequality. Activism plays a critical role in shaping policy and ensuring that tampons are accessible and affordable for all menstruators. Many advocacy groups campaign to remove sales tax on tampons and other menstrual products, arguing that these items are essential healthcare products rather than luxury goods. [ 102 ]  Success stories include states and countries that have already abolished the tax, setting a precedent for global change. [ 103 ]


Campaigns also work to normalize conversations about menstruation, dismantling stigma that has historically silenced discussions around menstrual products. Destigmatization efforts include public education campaigns, art installations, and social media movements aimed at reframing menstruation as a natural aspect of human health. [ 104 ]  Advocates are pushing for the portrayal of menstruation in mainstream media, emphasizing diverse menstruators’ experiences and highlighting the role of tampons in empowering individuals to manage their periods effectively.


Organizations like Period: The Menstrual Movement and Menstrual Equity for All are working to raise awareness about the need for inclusivity in menstruation-related discussions. Advocating for free menstrual products in schools, prisons, and public spaces, particularly in areas serving predominantly racialized populations, can help bridge gaps in access. Schools and healthcare providers must offer menstrual care that reflect the cultural challenges faced by diverse racial groups, ensuring that tampons are accessible to all.


Thinx  is a  New York –based company that sells  period underwear , an undergarment designed to be as absorbent as traditional  feminine hygiene  products. Since 2022,  Kimberly-Clark  has had a majority stake in the business.


Thinx was founded in 2011 by Antonia Saint Dunbar, Miki Agrawal, and Radha Agrawal. [ 1 ]  In 2018, Thinx released a new line called (BTWN), which offers period underwear for teens and  tweens . [ 2 ]  In June 2019, Thinx released Thinx Air, a quick-drying version of its underwear. [ 3 ]  As of 2021, Thinx has released its first activewear collection, which includes leggings, cycle shorts, training shorts, and  leotards  that are available in multiple colors. The four-piece collection functions like other Thinx underwear, but the  gusset  design is longer and shaped differently to accommodate active lifestyles. [ 4 ]  Miki Agrawal stepped down as CEO in 2017, after a former employee alleged that she had engaged in inappropriate office behavior. [ 5 ] [ 6 ]  Maria Molland took over as CEO, and under her leadership, Thinx was placed on shelves in  Target  and  Walmart .  [ 7 ]


In 2019,  Kimberly-Clark  made a minority investment in Thinx, and in February 2022, it acquired a majority stake in the company. [ 8 ]  In May 2022, Maria Molland stepped down as CEO, and the company appointed Meghan Davis as its new CEO. [ 9 ]


In 2020, lawsuits were filed against Thinx alleging misleading marketing following an independent test of the company's products that revealed the presence of  per- and polyfluoroalkyl substances  (PFAS), a type of chemical found in consumer products and linked to numerous long-term health risks. [ 10 ]  The lawsuits called into question whether Thinx marketing claim that its products were "organic, sustainable and nontoxic" was deceptive. In May 2022, the lawsuits were combined into a proposed  class action , and the company reached a settlement in the case in November. In January 2023, the terms of the settlement were announced to consumers, which included no admission of wrongdoing and the company agreeing to pay up to US$5 million to consumers. Thinx also put out a statement alleging that PFAS are not part of the product design and going forward, it would ensure PFAS are not added to its products. [ 11 ] [ 12 ]


On January 29, 2024, CEO Meghan Davis announced on a company-wide Zoom call that 95 of the 109 staff members would be losing their jobs on May 1. Five of the laid-off employees were offered positions as employees of  Kimberly-Clark , Thinx's parent company. [ 7 ]


Thinx underwear comes in a range of styles from  boyshorts  to  thongs  and includes two patented technologies. One is to absorb different amounts of blood, [ 13 ]  and the other absorbs different amounts of urine. The underwear has been reported as being antimicrobial, moisture-wicking, absorbent, and leak resistant. [ 14 ]  In 2019, Thinx launched Thinx Super, which is a double-absorbency product that claims to hold up to four tampons' worth of flow. [ 15 ]  The underwear cost about $35 per pair. [ 7 ]  Thinx introduced a pair that cost $17 in order to better compete with new lines of period underwear from large brands like  Aerie  and  Hanes . [ 7 ]


Thinx earned a reputation for its controversial ads. [ 16 ]  In October 2015,  Outfront Media  rejected Thinx's subway advertisements due to the fact that the ads used the word "period" and included suggestive visuals of food. [ 17 ] [ 18 ]  Following a social media outcry, the ads were finally allowed to be shown. [ 19 ] [ 20 ]  In 2016, Thinx received attention for featuring trans male models in its ads for period underwear. [ 21 ] [ 22 ]  In November 2016, Thinx launched an ad referencing the  Donald Trump  Access Hollywood  tape . The San Francisco subway banned the ads due to the use of the word "pussy". [ 23 ] [ 24 ]  In November 2017, they created a "PMS truck", a truck visiting three cities, allowing visitors to step inside to shop for Thinx products and talk with brand representatives regarding period health. [ 25 ]  In 2019, Thinx rolled out a national ad campaign featuring a young boy getting his first period with the tagline: "What if we all had periods?" and subsequent campaigns focused on reducing period stigma by showcasing men. [ 26 ] [ 27 ]  These ads were banned by several TV networks including CBS for being "too graphic". [ 28 ]


After 2019, employees noticed that Thinx's marketing direction changed, featuring fewer images of people in underwear, and treating periods like something to hide. [ 7 ]  In 2022, a television showed a mom starting to demonstrate tampon use to her daughter before a sister interrupts the scene with Thinx underwear, saying "Mom won't have to show you how to use them." Employees felt that Thinx's advertising no longer destigmatized  menstruation . [ 7 ]


TIME  named Thinx  period panties  as one of the best inventions of 2015. [ 29 ]   Fast Company  named Thinx one of the most innovative companies of 2017, pointing to founder Agrawal's promotional campaigns and her application of "high-tech merchandise, considered design, and a rule-breaking philosophy" to launches of new products. [ 30 ]


In 2019 Thinx leaders signed a letter condemning the abortion bans being put into place across the country. [ 31 ]


Vaginal flora ,  vaginal microbiota  or  vaginal microbiome  are the  microorganisms  that colonize the  vagina . They were discovered by the German gynecologist  Albert Döderlein  in 1892 [ 1 ]  and are part of the overall  human flora .
The amount and type of bacteria present have significant implications for an individual's overall health. [ 2 ]   The primary colonizing bacteria of a healthy individual are of the genus  Lactobacillus , [ 3 ]  such as  L. crispatus , and the  lactic acid  they produce is thought to protect against infection by pathogenic species. [ 4 ]


The primary colonizing bacteria of a healthy individual are of the genus  Lactobacillus  (90–95%), the most common being  L. crispatus ,  L. iners ,  L. jensenii , and  L. gasseri . [ 5 ]  Since the first description of lactobacilli by Döderlein, lactobacilli have been generally considered the gatekeepers of the vaginal ecosystem. Lactobacilli have been shown to inhibit in vitro growth of pathogenic microorganisms, e.g.  Bacteroides fragilis ,  Escherichia coli ,  Gardnerella vaginalis ,  Mobiluncus  spp. ,  Neisseria gonorrhoeae ,  Peptostreptococcus anaerobius ,  Prevotella bivia  and  Staphylococcus aureus . It is generally accepted that this is achieved mainly through the action of lactic acid. [ 6 ] [ 7 ] [ 8 ] [ 9 ]  Moreover, lactobacilli normally help to prevent long-term colonization of the vagina by adhering to vaginal epithelial cells. This usually reduces pathogens from infecting  to the  vaginal epithelium . [ 10 ]


Next to lactic acid production and competition for adherence, other antagonistic mechanisms include  hydrogen peroxide  (a broad-spectrum antimicrobial) and  bacteriocins  (target-specific antimicrobials) production. [ 11 ] [ 12 ]


Low pH is generally accepted to be the main mechanism controlling the composition of the vaginal microflora. Although the lactic acid produced by lactobacilli contributes to the vaginal acidity, it is still not proven to be the primary source of low vaginal pH, but the fact remains that most lactobacilli thrive best at a pH < 3.5 . [ 13 ] [ 14 ] [ 15 ]
Normal vaginal pH is considered to be under 4.5 with a range of 3.8 to 4.4. [ 5 ]


Production of hydrogen peroxide (H 2 O 2 ) is a proposed mechanism for bacterial antagonism in vitro, [ 16 ] [ 17 ] [ 18 ]  inhibiting growth of microorganisms via direct interaction or via human myeloperoxidase. [ 19 ] [ 20 ] [ 21 ]  However, in vivo, the role of peroxide is uncertain. Under optimal anaerobic growth conditions, physiological concentrations of lactic acid inactivated the  BV-associated pathogens  without affecting the vaginal lactobacilli. [ 12 ] [ 22 ]  Although the hydrogen peroxide production of lactobacilli has been considered as an important antimicrobial component, contributing to the colonization resistance provided by lactobacilli, [ 11 ] [ 23 ]  and although there seems to be a link between H 2 O 2 -producing lactobacilli and normal vaginal microflora, recent data do not support this role for H 2 O 2 . [ 12 ] [ 22 ]


Experimentally, hydrogen peroxide-producing lactobacilli have been shown to inactivate  HIV-1 ,  herpes simplex virus type 2  (HSV-2),  Trichomonas vaginalis ,  G. vaginalis ,  P. bivia  and  E. coli . O'Hanlon [ 12 ]  and Baeten [ 24 ]  found that 96% of  Lactobacillus  species from a healthy vaginal ecosystem produced H 2 O 2  ( L. jensenii  and  L. vaginalis  produce the highest levels of H 2 O 2 ), [ 11 ] [ 25 ]  whereas only 6% of the lactobacilli recovered from women with BV produced H 2 O 2 . [ 19 ]  In agreement with this,  L. iners , most frequently associated with disturbed vaginal microflora, [ 26 ] [ 27 ]  is a poor producer of H 2 O 2 . [ 28 ] [ 29 ]  Vaginal colonization by H 2 O 2 -producing lactobacilli has been associated with a decrease in the occurrence of  bacterial vaginosis  (BV). [ 30 ]  However, more recently O'Hanlon et al. [ 22 ]  demonstrated that cervicovaginal fluid and semen have a significant H 2 O 2 -blocking activity and they later  [ 12 ]  demonstrated that physiological concentrations of H 2 O 2  below 100 μM fail to inactivate any of the 17 tested BV-associated bacteria, e.g.  A. vaginae ,  G. vaginalis ,  Mobiluncus  spp. ,  P. bivia ,  P. corporis ,  Mycoplasma hominis , even in the presence of human  myeloperoxidase , known to increase the microbicidal activity of H 2 O 2 . [ 12 ]  Only supraphysiologic concentrations of exogenous H 2 O 2  (0.34% w/v, 100 mM) were sufficient to inactivate BV-associated bacteria at which concentration it more potently inactivated vaginal lactobacilli ( L. crispatus ,  L. gasseri ,  L. iners  and  L. jensenii ). A concentration of 100 mM H 2 O 2  is approximately 50-fold higher than lactobacilli are capable of producing even under optimal aerobic, low-antioxidant conditions, and approximately 5,000-fold higher than the estimated H 2 O 2  concentration in vivo. Even more remarkable, the addition of only 1% vaginal fluid blocked the microbicidal activity of 1 M H 2 O 2 . Possible explanations may be that cervicovaginal fluid and semen contain proteins, glycoproteins, polysaccharides, lipids, and other molecules with the potential to react with and inactivate H 2 O 2 . In addition, the vagina is hypoxic most of the time, whereas lactobacilli require oxygen to produce hydrogen peroxide. It is also remarkable that catalase, which provides bacteria protection against toxic H 2 O 2 , is absent in lactobacilli, [ 19 ] [ 31 ]  and as such they would be unprotected against their own H 2 O 2  production. Consequently, hydrogen peroxide production may not be the major mechanism of defense.


Vaginal lactobacilli produce antimicrobial peptides, i.e. bacteriocins such as lactocin 160 and crispasin. [ 13 ]  with inhibitory activity ranging from narrow (closely related  Lactobacillus  species) to broad (diverse groups of bacteria, including  G. vaginalis  and  P. bivia ), [ 8 ]  and bacteriocin-like substances, with a broader spectrum of activity than bacteriocins (e.g. a heat-resistant peptide produced by  Ligilactobacillus salivarius  subsp.  salivarius  CRL 1328). Several studies have indicated that the activity of bacteriocins is favored by low pH.


The inhibitory substances produced by vaginal  Lactobacillus  is a primary factor in protecting the vaginal microbiota, with organic acids, bacteriocins, and hydrogen peroxide. These act synergistically against infection by pathogens. Not all  Lactobacillus  spp. and not all strains within one  Lactobacillus  species exhibit all 3 mechanisms. [ 13 ]   Lactobacillus  species differ in premenopausal women, i.e.  L. crispatus ,  L. jensenii ,  L. iners ,  L. gasseri  (and possibly  Limosilactobacillus vaginalis ), as assessed through cultivation-dependent and cultivation-independent techniques. [ 26 ] [ 27 ] [ 28 ] [ 32 ]  Vaginal lactobacilli have been shown to display a pronounced vaginotropism, and their pili act as ligands for attachment to receptors of vaginal epithelial cells. The limited number of  Lactobacillus  spp. found in the human vagina is remarkable, which leads to the possibility that there are host factors that select for specific organisms, that these species
have unusual characteristics that allow them to successfully colonize the vagina, or both
. [ 33 ]  However, the vaginotropism, does not only apply to this selected group of lactobacilli
that stand for a healthy vagina, but also for the bacterial species associated with BV. [ 34 ]  The microbiota detected in the human genital and gut econiche do not appear to grow outside their
host and probably are likely to rely on the close contact between parents and their children for transmission, [ 34 ]  e.g. mother to neonate transmission of genital microflora, most probably also with gut microflora homogenously distributed over the baby's body including skin, the oral cavity, nasopharynx, and feces. [ 35 ]


Bacterial vaginosis  (BV) is associated with the presence of  Gardnerella vaginalis  and  Peptostreptococcus anaerobius [ 36 ]  and a decrease in the number of  Lactobacillus  species that comprise the healthy vaginal microbiota. [ 37 ] [ 38 ] [ 39 ] [ 40 ]  BV is characterized by overgrowth of opportunistic bacteria and a decrease in Lactobacillus species. BV can present itself as symptomatic or asymptomatic. Symptoms include vaginal malodor, increased vaginal pH, and vaginal itching.  [ 41 ]  There is no one known cause as to why BV occurs but it is typically associated with abnormal vaginal discharge (Coudray & Madhivanan, 2020).  To diagnose BV in a clinical setting, an Amsel's criteria is used. This means that a patient must have an increased homogeneous thin vaginal discharge, pH secretion higher than 4.5, amine odor when secretions are exposed to hydroxide 10% solution, or clue cells visible on a wet mount. Another way to diagnose BV that is less often used in a clinical setting is a Nugent score. To obtain a Nugent score, gram stain techniques are carried out and it characterizes the bacterial morphology on a scale. A score greater than 7 is associated with BV, 4-6 is an intermediate abnormality, and 0-3 is normal. [ 42 ]  Typically, only women with symptoms receive treatment. Treatment include antibiotics, specifically metronidazole and clindamycin (Hay, 2010).


Studies have shown a correlation between vaginal microbiota and BV development through 16S RNA sequencing. Community state types (CSTs) are used to identify variation between a healthy vaginal microbiota and vaginal microbiota of someone with BV. Most CSTs in a healthy vaginal microbiome consist of different species of  Lactobacillus.  Studies found that  L.iners  is the dominant species in BV and  L.crispatus  is the dominant species in healthy vaginal microbiomes. [ 43 ]


Healthy,  normal vaginal microbiota that is dominated by lactobacilli may differ among some ethnic groups.  Non-pathogenic  vaginal species are part of the normal microbiota of some women. [ 26 ] [ 44 ]  Several studies have demonstrated that a significant proportion (7–33%) of healthy asymptomatic women (especially black and Hispanic women) [ 45 ]  lack appreciable numbers of Lactobacillus species in the vagina, [ 33 ] [ 46 ]  and instead have a vaginal microbiota that consist of other lactic acid-producing bacteria, i.e. species from the genera  Atopobium ,  Leptotrichia ,  Leuconostoc ,  Megasphaera ,  Pediococcus ,  Streptococcus  and  Weissella , [ 32 ] [ 33 ] [ 45 ]   All ethnic populations have vaginal microflora communities containing lactic acid producing bacteria. [ 33 ] [ 45 ]  This implies that not all communities may be equally resilient, so that if the resilience of a vaginal community is low then transitory changes in the structure of these communities may occur more readily in response to disturbances of various kinds, including  menses , sexual intercourse, douching and contraceptive practices. These differences in the structure and composition of microbial communities may underlie well-known differences in the susceptibility of women in these racial groups to BV and various vaginal infections. [ 45 ] [ 47 ] [ 48 ]  Though vaginal microflora may be disturbed, and lactic acid is produced by other species, [ 49 ]  vaginal pH and acid production establish normal vaginal microbiota. The pH further decreases during pregnancy. [ 50 ]


Other bacterial species are frequently found in the vagina, such as the Gram positive cocci:  Atopobium vaginae ,  Peptostreptococcus  spp. ,  Staphylococcus  spp. ,  Streptococcus  spp. , and  Bacteroides  spp. ,  Fusobacterium  spp. ,  Gardnerella vaginalis ,  Mobiluncus ,  Prevotella  spp. , and  Gram-negative enteric organisms , such as  Escherichia coli . [ 26 ] [ 27 ]   Mycoplasma  and  Ureaplasma  are frequently found in the vagina. Some of the obligate and facultative anaerobic bacteria are associated with BV. [ 46 ]   Neisseria gonorrhoeae  is found in the vagina and is considered a  pathogen  that is sexually transmitted. [ 51 ]


The effect of  tampon  use on vaginal flora is debated, but application of tampons appears not to significantly modify the balance of bacterial presence. [ 52 ]  Pregnancy alters the microbiota with a reduction in species/genus diversity. [ 37 ]


A healthy vaginal microbiome aids in the prevention of bacterial vaginosis,  yeast infections  and other possible problems by maintaining an acidic pH (< 4.5) that is unfavourable for the growth of common pathogens, such as  Gardnerella vaginalis . The lactobacilli present in a healthy vaginal microbiome also occupy the  ecological niche  that would otherwise be available for exploitation by pathogenic organisms. However, harmful bacteria or an imbalance in bacteria can lead to infection. [ 53 ]


There are many factors that contribute to the composition of vaginal microbiota including stress, age, lifestyle, diet, gut microbiota, antibiotics, probiotics, and vaginal infections.


Lifestyle can impact microbiota by means of personal hygiene. Research suggests that vaginal douching is associated with increased risk of BV. It also shows that sexual practices that include multiple sexual partners can increase BV or throw off stable microbiota composition. [ 54 ]  Smoking and alcohol consumption can also increase likelihood of BV development because it indirectly impacts the metabolite production profile. [ 55 ]  There is also research supporting the idea that increased stress levels can have an impact on the balance of vaginal lactobacilli by elevating cortisol levels, reducing vaginal glycogen, lowering lactobacilli, elevating vaginal pH, and increasing proinflammatory response. [ 54 ]


It is becoming more commonly known how our diets can impact our gut microbiota, but it can have the same impact on vaginal microbiota. Research shows that diets rich in nutrients with low glycemic index and lower fat intake may be associated with a decreased chance of getting BV. [ 54 ]


Investigations have found that the presence of lactobacilli in the vagina is associated with a lower incidence of sexually transmitted infections. [ 56 ] [ 57 ]


The  vaginal flora in pregnancy , or  vaginal microbiota in pregnancy , is different from the  vaginal flora  (the population of microorganisms that resides in the vagina) before  sexual maturity , during reproductive years, and after  menopause . A description of the vaginal flora of pregnant women who are  immunocompromised  is not covered in this article. The composition of the vaginal flora significantly differs in  pregnancy . [ 1 ]  Bacteria or viruses that are infectious most often have no symptoms.


In normal pregnancy, the resident vaginal flora is thought to provide protection against infection. The microbiota during pregnancy are predominantly  Lactobacillus  species. Microbiota composition can change during the course of the pregnancy. If the microbiota populations become more diverse, indicating that the normal  Lactobacillus -dominated population has changed to a bacterial vaginosis population, risks of adverse pregnancy outcomes increase. [ 2 ]  Vaginal discharge is common during pregnancy but is not an indicator of bacterial vaginosis or abnormal microbiota. [ 3 ]  The treatment of abnormal vaginal microbiota populations with lactobacilli and estriol during pregnancy was found to restore the microbiota to a normal state. [ 4 ]


During pregnancy, the vaginal microbiome can contribute and play an important role in spontaneous and preterm labor. The transmission of the flora from mother to children occurs via the vagina, breast milk, and the maternal gut. After the mother has given birth to her child, the  Lactobacillus -rich microbiome drops significantly, and it becomes more diverse during the postpartum period. [ 5 ]


During pregnancy, the pH is altered due to excessive vaginal discharge, and this alters the microbiota that is present in the vagina. The bacterial species  Firmicutes  and  Actinobacteria  are identified in dysbiotic states such as this one. [ 5 ]


Bacterial vaginosis  in pregnancy is an alteration of the normal vaginal microbiota of pregnancy. Intrauterine infections in pregnancy are caused by bacteria that cause inflammation. The women may experience few or no symptoms. This sometimes leads to  chorioamnionitis  and other negative pregnancy outcomes. Chorioamnionitis is due to the presence of bacteria such as  Ureaplasma parvum  and  Mycoplasma  species this generates the release of proinflammatory cytokines and chemokines, IL-8 which causes cervical ripening and can result in premature birth. [ citation needed ]  When there are high bacterial counts in of the vagina during pregnancy is typically due to the presence of the following organisms: [ 3 ]


A major portion of the vaginal microbiome also includes vaginal viral virome. According studies that have been done so far, it can be seen that there are an abundance of ds DNA viruses, ss DNA viruses and some unidentified viruses that are part of the vaginal microbiome. Only few eukaryotic viruses were detected. Out of the ones that were detected, the pathogenic viruses were  Herpesvirales  and  Papillomaviridae . [ 5 ]


There are racial variations that are present in microbiomes between women of different races. Women who belong to Asian, White, and Caucasian race have be observed to have more anaerobic flora. The dominant member in the microbiome of these women is  Lactobacillus . Women who are Hispanic and Black have anaerobic bacteria, but the dominant member of their microbiomes is not  Lactobacillus . Black females are seen to have single-species dominant cluster, while Caucasian women have multiple species of  Lactobacillus  present in their microbiome. [ 5 ]


Racial diversity is just of the few factors that is known to influence the variation in microbiomes in women. Other factors that also influence the variation in microbiomes are health, sexual partner, mother being a diabetic or not, and variation between monozygotic and dizygotic twins. All of different modes of delivery of microbiome from the mother to the infant, vaginal delivery can be seen to be the most favorable. [ 5 ] [ 6 ]


Vaginal microbiomes are affected and influenced by many exogenous and endogenous factors. These factors can include contraceptive agents, using antibiotics, vaginal douching, and pregnancy. Abnormal vaginal flora (AVF) is when there is an overgrowth and colonization of pathogenic microorganisms. This includes microorganisms that cause infections such as vulvo-vaginal candidiasis (VVC), bacterial vaginosis (BV), cytolytic vaginosis (CV), intermediate flora and mixed vaginitis, and trichomoniasis. [ 6 ]


Studies shows that AVF can be one of the contributing risk factors in gynecological complications. There complications include sexually transmitted diseases and pelvic inflammatory disease. AVF has also been associated with issues such as premature rupture of membranes, preterm birth, ascending intrauterine infections, and other adverse outcomes of pregnancy. [ 6 ]


Investigations into reproductive-associated microbiomes began around 1885 by  Theodor Escherich . He wrote that  meconium  from the newborn was free of bacteria. This was interpreted as the uterine environment was sterile. Other investigations used sterile diapers for meconium collection. No bacteria were able to be cultured from the samples. Bacteria were detected and were directly proportional to the time between birth and the passage of meconium. [ 7 ]


Vagisil  is an American brand of  over-the-counter  cream used to treat external vaginal itching and irritation. It is produced by  Combe Incorporated , a company based in  White Plains, New York  and was introduced in 1974. [ 1 ]


The active ingredients are  benzocaine  (5%), a local anesthetic which reduces the itching, and  resorcinol  (2%), an antiseptic which treats the skin irritation. [ 2 ]


In February, 2021, Vagisil launched new products labelled  OMV!  which are scented wipes, cleansers and anti itch creams for  vaginas  and  vulvas . The marketing is directed at teenagers, which has been criticized on social media by doctors.  OB/GYNs   Jen Gunter , Chavone Momon-Nelson and Jocelyn Fitzgerald all expressed worry that the advertising campaign will make teens ashamed of their vaginas and that the treatment will cause issues such as irritation and allergic reaction. They worry that the teens may not seek medical advice for real issues, such as yeast infections that should not be treated with Vagisil. Gunter and Momon-Nelson agree that the vagina should be left alone and does not need special cleaners or refreshing. Vagisil responded to this criticism explaining that their products have an appropriate pH level for external use in the vulvar area and have been tested by independent  dermatologists  and  gynecologists . [ 3 ]  A spokesperson for Vagisil stated that their products are not for everyone and that they created  OMV!  in response to active young women who have expressed "...worry about period hygiene and odours". Gunter counters stating menstruation is natural and vaginas are not supposed to smell like the  OMV!  scents roses or vanilla-clementine. [ 4 ]


Vagisil has been the subject of various comedy routines.


In the  South Park  episode " Poor and Stupid "  Cartman  sees a commercial for Vagisil which lists  short-term memory loss  as a possible side effect. He then goes to a pharmacy with  Butters Stotch  to consume large quantities of the cream in an attempt to become "dumb enough" to perform well in  NASCAR  races.


Vagisil appears as an alleged sponsor of "Ladies' Bowling" in a series of sketches on the TV show  Saturday Night Live . One of the sports commenters in the sketches repeatedly advertises the product with highly inappropriate marketing slogans.


In the TV show  The Big Bang Theory ,  a Vagisil coupon that came in the mail to Sheldon Cooper appears at the end of the second episode of the seventh season, which he presents as a gift to Penny with a comment: "Think of me when you apply it".


In the movie  Major League ,  aging Starting Pitcher Eddie Harris illegally uses Vagisil to increase the drop on his " Curveball ".


For  fertilization  to happen between a  sperm  and  egg cell , a sperm must first fuse with the plasma membrane and then penetrate the female egg cell to fertilize it. While the fusion of the sperm cell with the egg cell's plasma membrane is relatively straightforward, penetrating the egg's protective layers, such as the zona pellucida, presents a significant challenge. Therefore, sperm cells go through a process known as the  acrosome  reaction, which is the reaction that occurs in the acrosome of the sperm as it approaches the egg.


The acrosome is a membrane-bound organelle of Golgi apparatus origin, commonly located at the tip of the head of the mature spermatozoon, which contains a variety of enzymes and antigens required for fertilization. It was once called "apical body" because of its location, or "perforatorium" on the assumption that it might assist the spermatozoon boring into the egg. [ 1 ]


As the sperm approaches the  zona pellucida  of the egg, which is necessary for initiating the acrosome reaction, the membrane surrounding the acrosome fuses with the  plasma membrane  of the sperm's head, exposing the contents of the acrosome. The contents include surface antigens necessary for binding to the egg's cell membrane, and numerous enzymes which are responsible for breaking through the egg's tough coating and allowing fertilization to occur. [ 2 ]


There are considerable species variations in the morphology and consequences of the acrosome reaction. In several species, the trigger for the acrosome reaction has been identified in a layer that surrounds the egg.


In some lower animal species, a protuberance (the acrosomal process) forms at the apex of the sperm head, supported by a core of actin microfilaments. The membrane at the tip of the acrosomal process fuses with the egg's plasma membrane.


In some echinoderms, including  starfish  and  sea urchins , a significant portion of the exposed acrosomal content contains a protein that temporarily holds the sperm on the egg's surface.


In mammals, the acrosome reaction releases  hyaluronidase  and  acrosin ; their role in fertilization is not yet clear. The acrosomal reaction is initiated when sperm comes into contact with the oocyte's  zona pellucida . Upon coming into contact with the zona pellucida, the acrosomal enzymes begin to dissolve, and the actin filament comes into contact with the zona pellucida. Once the two meet, a calcium influx occurs, causing a signaling cascade. The cortical granules inside the oocyte then fuse to the outer membrane, and a quick fast block reaction occurs.


Furthermore, the cortical granules inside the oocyte fuse with the outer membrane, initiating a rapid block reaction. This reaction alters a patch of pre-existing sperm plasma membrane, facilitating fusion with the egg plasma membrane.


A sperm penetration assay includes an acrosome reaction test that assesses how well a sperm can perform during the fertilization process. Sperm that are unable to go through the acrosome reaction properly will not be able to fertilize an egg. However, this problem only occurs in about 5% of men that have the test done. This test is rather expensive and provides limited information on a man's fertility. [ 3 ]


In other cases, such as in the  wood mouse Apodemus sylvaticus , premature acrosome reactions have been found to cause increased motility in aggregates of spermatozoa promoting fertilization. [ 4 ]


The acrosomal reaction typically occurs in the  ampulla  of the  fallopian tube , the site of fertilization, when the sperm penetrates the secondary oocyte. Prior events prepare for the acrosome reaction. The sperm cell undergoes a series of changes, including acquiring a "hyperactive motility pattern" where its flagellum produces vigorous whip-like movements propelling the sperm through the cervical canal and uterine cavity until it reaches the isthmus of the fallopian tube. Various mechanisms, including chemotaxis, aid the sperm in approaching the ovum in the ampulla of the fallopian tube. Once in close proximity, glycoproteins on the outer surface of the sperm bind with glycoproteins on the  zona pellucida  of the ovum.


Sperm that fail to initiate the acrosome reaction prior to reaching to the zona pellucida are unable to penetrate the zona pellucida. Since the acrosome reaction has already occurred, sperm are then able to penetrate the zona pellucida due to mechanical action of the tail, not because of the acrosome reaction itself. [ 5 ]


The first stage is the penetration of corona radiata, by releasing hyaluronidase from the acrosome to digest cumulus cells surrounding the oocyte and exposing acrosin attached to the inner membrane of the sperm. The  cumulus cells  are embedded in a gel-like substance made primarily of  hyaluronic acid , and developed in the ovary with the egg and support it as it grows. The acrosome reaction must occur before the sperm cell reaches the zona pellucida. [ 5 ]


Acrosin, once exposed, digests the zona pellucida and membrane of the oocyte, allowing for penetration to happen. Part of the sperm's cell membrane then fuses with the egg cell's membrane, and the contents of the head sink into the egg. In the mouse, it has been demonstrated that ZP3, one of the proteins that make up the zona pellucida, binds to a partner molecule (to the β1,4-galactosyl transferase receptors) on the sperm. This lock-and-key type mechanism is species-specific and prevents the sperm and egg of different species from fusing. The zona pellucida also releases Ca granules to prevent other sperm from binding. There is some evidence that this binding is what triggers the acrosome to release the enzymes that allow the sperm to fuse with the egg. A similar mechanism likely occurs in other mammals, but the diversity of zona proteins across species means that the relevant protein and receptor may differ.


More recent scientific evidence demonstrates that the acrosomal reaction is necessary to expose a protein called  IZUMO1  on the sperm: without the reaction, sperm can still penetrate through the zona pellucida to the egg membrane, but cannot fuse. [ 6 ]  As seen in mouse studies, IZUMO1 binds to the oocyte protein  JUNO  and once bound together, the sperm and the egg fuse together to form two pronuclei. [ 7 ] [ 8 ]  These pronuclei supply the zygote with the genetic material necessary for the formation of an embryo.  Additionally, once the fusion of the sperm and oocyte is complete, phospholipase C zeta is released from the sperm.


Following penetration and fusion, if all is normally occurring, the process of egg-activation occurs facilitated by proteins like phospholipase C zeta, and the oocyte is said to have become  activated . This is thought to be induced by a specific protein phospholipase c zeta. It undergoes its secondary meiotic division, and the two haploid nuclei (paternal and maternal) fuse to form a  zygote . To prevent  polyspermy  and minimize the possibility of producing a  triploid  zygote, several changes to the egg's cell membranes render them impenetrable shortly after the first sperm enters the egg (such as the rapid loss of JUNO). [ 8 ]


Spermatozoa can initiate the acrosomal reaction well in advance of reaching the zona pellucida, as well as  in vitro  in an appropriate culture medium. This is referred to as spontaneous acrosome reaction (SAR).


It is now known that, in a certain sense, this phenomenon is physiologically normal across mammalian species. The acrosome reaction is induced by passage through the  cumulus oophorus  cells, mediated by the hormones they secrete (such as  progesterone ,  LPA ,  LPC ). [ 6 ] [ 9 ] [ 10 ]


However, the physiological role of truly spontaneous acrosomal reaction, occurring well before this point in the female reproductive tract, or  in vitro , is a separate phenomenon.


In mice, it has been well established as physiologically normal and common. Mouse sperm which have undergone fully spontaneous acrosome reaction are still able to fertilize eggs. [ 6 ]  Furthermore, the rate of spontaneous acrosome reaction is higher in more promiscuous species such as  Apodemus sylvaticus , which face a high level of sperm competition. [ 11 ]


In humans, on the other hand, it remains disputed where exactly the acrosome reaction is initiated in physiological fertilization, due to experimental constraints (for example, animal studies may make use of  transgenic mice  with fluorescent sperm, while human studies cannot). [ 10 ]


Studies have been done with the intent of linking  in vitro  SAR rate in human sperm to sperm quality and fertilization rate, but as of 2018, the overall results have been mixed, and do not seem to be clinically informative. [ 12 ]


When using  intracytoplasmic sperm injection  (ICSI) for  IVF , the  implantation rate  is higher in oocytes injected with spermatozoa that have undergone acrosome reaction (~40%) vs. those injected with nonreacted spermatozoa (~10%). The implantation rate is ~25% in when injected with both reacted and nonreacted spermatozoa. The  delivery rate  per cycle follows the same trend. [ 13 ]


The acrosome reaction can be stimulated in vitro by substances a sperm cell may encounter naturally, such as  progesterone  or  follicular fluid , as well as the more commonly used calcium  ionophore   A23187 .


Birefringence  microscopy, [ 13 ]   flow cytometry [ 14 ]  or  fluorescence microscopy  can be used for assessing the shedding of the acrosome or "acrosome reaction" of a sperm sample. Flow cytometry and fluorescence microscopy are usually done after staining with a fluoresceinated  lectin  such as FITC-PNA, FITC-PSA, FITC-ConA, or fluoresceinated antibody such as FITC-CD46. [ 15 ]  The antibodies/lectins have a high specificity for different parts of the acrosomal region, and will only bind to a specific site (acrosomal content/ inner/outer membrane). If bound to a fluorescent molecule, regions where these probes have bound can be visualised. Sperm cells with artificially induced acrosome reactions may serve as positive controls.


For fluorescence microscopy, a smear of washed sperm cells is made, air-dried, permeabilized, and then stained.  Such a slide is then viewed under the light of a wavelength that will cause the probe to fluoresce if it is bound to the acrosomal region.  At least 200 cells are considered arbitrarily and classified as either acrosome intact (fluorescing bright green), or acrosome reacted (no probe present, or only on the equatorial region).  It is then expressed as a percentage of the counted cells.


For assessment with flow cytometry, the washed cells are incubated with the chosen probe, possibly passed again, then sampled in a flow cytometer.  After gating the cell population according to forward- and side-scatter, the resulting data can be analyzed (E.g. mean fluorescences compared).  With this technique, a probe for viability such as  propidium iodide  (PI) could also be included in order to exclude dead cells from the acrosome assessment, since many sperm cells will spontaneously lose their acrosome when they die.


Andrology  (from  Ancient Greek :  ἀνήρ ,  anēr ,  genitive   ἀνδρός ,  andros  'man' and  -λογία ,  -logia ) is a name for the  medical specialty  that deals with  male  health, particularly relating to the problems of the  male reproductive system  and  urological  problems that are unique to  men . It is the parallel to  gynecology , which deals with medical issues which are specific to female health, especially reproductive and urologic health.


Andrology covers anomalies in the connective tissues pertaining to the genitalia, as well as changes in the volume of cells, such as in genital hypertrophy or macrogenitosomia. [ 1 ]


From reproductive and urologic viewpoints, male-specific medical and  surgical procedures  include  vasectomy ,  vasovasostomy  (one of the vasectomy reversal procedures),  orchidopexy ,   circumcision , sperm/ semen cryopreservation , surgical sperm retrieval, semen analysis (for fertility or post-vasectomy), sperm preparation for  assisted reproductive technology  (ART) as well as intervention to deal with male genitourinary disorders such as the following:


Unlike gynaecology, which has a plethora of medical board certification programs worldwide, andrology has none. Andrology has only been studied as a distinct specialty since the late 1960s: the first specialist journal on the subject was the German periodical  Andrologie  (now called  Andrologia ), published from 1969 onwards. [ 2 ]  The next specialty journal covering both the basic and clinical andrology was the  International Journal of Andrology , established in 1978, which became the official journal of the European Academy of Andrology in 1992. In 1980 the American Society of Andrology launched the  Journal of Andrology . In 2012, these two society journals merged into one premier journal in the field, named  Andrology , with the first issue published in January 2013. [ 3 ]


Antisperm antibodies  ( ASA ) are  antibodies  produced against  sperm   antigens .


Antisperm antibodies are  immunoglobulins  of  IgG ,  IgA , and/or  IgM , which are directed against  sperm   antigens . ASA can be detected in ejaculate, cervical mucus, follicular fluid, and  blood serum  of both males and females. [ 1 ]  While IgG and IgA might be present in blood serum and/or genital tract fluids, IgM is only present in blood serum. IgG occurring in genital tract fluids is either produced locally or transuded from blood serum, whereas IgA (secretory type) is always produced locally. [ 2 ]


Traditionally, the breakdown of the  blood-testis barrier  had been established as the cause of ASA production. This mechanism had been advocated in testicular trauma and surgery,  orchitis  ( mumps ),  varicocele , bacterial infections ( epididymitis ,  prostatitis ),  testicular cancer , and unprotected  anal intercourse . However, the association between aforementioned conditions and ASA production is controversial. [ 2 ]  Only chronic obstruction, most typically represented by  vasectomy  followed by  vasectomy reversal , is the only one condition leading constantly to high and permanent ASA titers. [ 3 ]  Apart from breaching of blood-testis barrier, epididymal distension, raised intraluminal pressure, and sperm  granuloma  formation leading spermatozoal  phagocytosis  seem to be contributing factors. [ 4 ]


As of 2017, it is unclear how or why women generally do not develop ASA, and why some women do develop them; the clearest correlations are that women whose male partners have ASA in their semen are more likely to have ASA, and women with ASA tend to react only to their partner's sperm and not to other men's sperm. [ 5 ] : 161  [ 6 ]   The hypotheses for how women form ASA, as of 2017, includes cross-reactivity with microbial antigens, antibodies raised against ASA in their partner's semen, and a  cytokine -driven immune response to ASA in their partner's semen. [ 5 ] : 165–169   In women, spermatozoa in the genital tract after intercourse are not a factor in the production of antisperm antibodies. But this is possible with a trauma to the vaginal mucosa during the intercourse or the deposition of sperm in the gastrointestinal tract by oral or anal intercourse. [ 7 ] [ 8 ]


In both men and women, ASA production are directed against surface antigens on sperm, which can interfere with  sperm motility  and transport through the female reproductive tract, inhibiting capacitation and  acrosome reaction , impaired  fertilization , influence on the implantation process, and impaired growth and development of the  embryo . [ 1 ] [ 9 ]


Different tests have been developed to identify ASA in various biological substrates. However, only  Mixed Antiglobulin Reaction  (MAR) test and  Immunobead Test  (IBT) are currently being recommended by the WHO for the assessment of human sperm antibodies. [ 10 ]


MAR test in its original version is based on the classical  Coombs test ; sperm is mixed with human  red blood cells  coated with human IgG. A rabbit or goat  monospecific  anti-human IgG antibody is added.  Agglutination  (slow “shaky” movements) can be observed if sperm are coated with ASA. Instead of human red blood cells, commercial version of MAR test uses latex particles coated with human IgG ASA. Since the test is performed with fresh semen and the incubation requires only 10 minutes, it renders MAR test a quick and simple screening tool for ASA in human ejaculate. However, samples with very low sperm count (i.e. severe  oligoastheno -, or even  azoospermia ) cannot be evaluated using this method. Also presence of debris or high viscosity of semen can preclude its use. [ citation needed ]


IBT  is based on polyacrylamide spheres coated with rabbit anti-human immunoglobulins antibody. These particles are used either to identify ASA bound to sperm (direct IBT), or ASA present in various biological fluids – seminal plasma, cervical mucus, uterine, oviduct or follicular fluid (indirect IBT); the latter one requires addition of donor ASA-free sperm.


ASA might be present also in the cervical mucus of the female. These antibodies might be proved by the  postcoital test  (PCT). Although the test has been declared obsolete by some authors, it has still been widely used by many gynecologists. [ 11 ]  The test is performed 8–12 hours after an unprotected sexual intercourse at the estimated time of ovulation, when the cervical mucus is least viscous and thus most permeable for the sperm. The result is considered poor in case of less than 10 sperm per high power field are apparent.


Generally, the main drawback of all tests used for the diagnosis of ASA is a heterogeneity of data presented in available studies, caused by lack of method standardisation, various semen preparations, and inconsistent cut-off values. These facts compromise precise comparison between various methods. [ 2 ]


Since the precise etiology of ASA production is mostly unknown, causative treatment of ASA-mediated  infertility  is rarely possible.


Immunosuppressive therapy  comprising  corticosteroids  or  ciclosporin  has been proposed by several authors with promising results, nevertheless large randomized controlled trials failed to show a clear benefit. Owing to sometimes severe adverse effects, many clinicians are reluctant to treat immune infertile patients with above mentioned drugs.


In the clinical practice,  assisted reproductive techniques  are being considered as a golden standard for the immune-mediated infertility.


Albeit  intrauterine insemination  (IUI) might circumvent ASA present in the cervical mucus, in a study comprising 119 IUI, no live pregnancy was reported, suggesting involvement of other mechanisms of ASA. [ 12 ]  Since ASA are usually bound to sperm surface antigens with high affinity, ordinary wash-up used before ICSI is not effective. [ 2 ]  Thus, some authors recommend treatment of sperm with chymotrypsin/galactose to cleave ASA molecules. [ 13 ]  However, this method has not been adopted by clinicians as some concerns exist regarding a possible negative impact of this digestive enzyme on sperm surface receptors involved in fertilization. [ 14 ]


In vitro fertilization  (IVF) reaches lower  pregnancy rates  in ASA-positive individuals – basically, the higher ASA titers, the more negative outcome. This inverse association is more pronounced in ASA-positive males. [ 15 ]  It has been reported ASA binding to the sperm head have more negative impact on fertilization than those binding to the sperm midpiece or tail.


If  intracytoplasmic sperm injection  (ICSI) is added to IVF, similar outcome has been observed in both ASA-positive and ASA-negative couples. Nevertheless, one study showed significantly higher spontaneous pregnancy loss in the ASA-positives. [ 16 ]


ASA can arise whenever sperm encounter the immune system. [ 6 ]  ASA occur in women and men, including women or men who receive anal sex from men or who perform  oral sex  on men. [ 17 ] : 210  [ 7 ]


ASA have been considered as infertility cause in around 10–30% of infertile couples, and in males, about 12–13% (20,4% in meta-analysis) [ 9 ]  of all diagnosed infertility is related to an immunological reason.  The incidence can well be higher as the contribution to idiopathic infertility (31% of all cases) still remains elusive. However, these antibodies are also present in approximately 1–2.5 % of fertile men and in 4% of fertile women; the presence of ASA in the fertile population suggests that not all ASA cause infertility. [ 18 ] : 27   Only those antibodies directed against antigens involved in the fertilization process impair fertility. [ 2 ]


While around 75% of vasectomized men who have the process reversed by  vasovasostomy  have high levels of ASA in their blood, [ 19 ] : v   these circulating antibodies do not affect fertility in men; only ASA in the  male reproductive tract appears to do so. [ 20 ] : 134


About 40-45% of  sex workers  test positive for antisperm antibodies, compared to just 5% in the control group. [ 21 ]  Research has shown that these numbers increase for those who do not use contraceptive methods. [ 7 ]


There is a general effort to identify concrete sperm surface antigens which serve as a target for ASA. As sperm undergoes biological changes including  capacitation ,  acrosome reaction ,  zona  binding, and sperm-egg fusion, the set of sperm surface antigens is highly dynamic in time. Additionally, some of the sperm surface antigens might be incorporated into the  plasma membrane  of the embryo resulting in postfertilization negative impact of ASA. [ citation needed ]


Research has been conducted, but not clinically tested, to use sperm antigens or recombinant ASAs as  contraceptive vaccines  for humans, [ 22 ]  as well as captive and wild animals. [ 23 ]


The mechanisms through which both women and men develop ASA is also poorly understood and a subject of research. [ 5 ] : 161  [ 20 ] : 133


The  baculum  ( pl. :  bacula ), also known as the  penis bone ,  penile bone ,  os penis ,  os genitale , [ 1 ]  or  os priapi , [ 2 ]  is a  bone  in the  penis  of many  placental mammals . It is not present in humans, but is present in the penises of some  primates , such as the  gorilla  and the  chimpanzee . [ 3 ] [ 4 ]  The baculum arises from primordial cells in soft tissues of the penis, and its formation is largely influenced by  androgens . [ 5 ]  The bone lies above the  urethra , [ 6 ]  and it aids  sexual reproduction  by maintaining stiffness during  sexual penetration . The  homologue  to the baculum in  female mammals  is the baubellum ( os clitoridis ), a bone in the  clitoris . [ 7 ] [ 8 ] [ 9 ]


The word  baculum  means "stick" or "staff" in  Latin  and originates from  Greek :  βάκλον ,  baklon  "stick". [ 10 ]


The baculum is used for copulation and varies in size and shape by  species . Its evolution may be influenced by  sexual selection , and its characteristics are sometimes used to differentiate between similar species. [ 11 ]  A bone in the penis allows a male to mate for a long time with a female, [ 12 ] [ 13 ] [ 14 ]  which can be a distinct advantage in some  mating strategies . [ 15 ] [ 16 ]  The length of the baculum may be related to the duration of  copulation  in some species. [ 17 ] [ 18 ]  In carnivorans [ 19 ]  and primates, the length of the baculum appears to be influenced by  postcopulatory sexual selection . [ 20 ]  In some  bat  species, the baculum can also protect the  urethra  from compression. [ 21 ]


The baculum is absent in monotreme (egg-laying) and marsupial (pouch-bearing) mammals. Mammals having a penile bone include various  eutherians  (placental mammals):


Within Eutheria, the penile bone is absent in  ungulates  (hoofed mammals, including  cetaceans  (whales, dolphins, and porpoises)), [ 33 ]   elephants ,  lagomorphs , [ 25 ]   [ 34 ]   [ 26 ]  and  sirenians [ 6 ]  among others.


Evidence suggests that the baculum was independently evolved 9 times and lost in 10 separate lineages. [ 26 ]  The baculum is an exclusive characteristic of placentals and closely related eutherians, being absent in other mammal clades, and it has been speculated to be derived from the  epipubic bones  more widely spread across mammals, but notoriously absent in placentals. [ 35 ]


Among the primates,  marmosets , [ clarification needed ]  weighing around 500 grams (18 oz), have a baculum measuring around 2 millimetres (0.079 in), while the tiny 63 g (2.2 oz)  galago  has one around 13 millimetres (0.51 in) long. The great apes, despite their size, tend to have very small penis bones, and humans are the only ones to have lost them altogether. [ 16 ]


In some mammalian species, such as badgers [ 36 ] [ 37 ]  and raccoons ( Procyon lotor ), the baculum can be used to determine relative age. If a raccoon's baculum tip is made up of uncalcified cartilage, has a porous base, is less than 1.2 g (0.042 oz) in mass, and measures less than 90 mm (3.5 in) long, then the baculum belongs to a juvenile. [ 28 ]


Unlike most primates, humans lack a baculum, [ 38 ] [ 39 ]  but the bone is present, although much reduced, among other  great apes . In many ape species, it is a relatively insignificant 10–20 mm (0.39–0.79 in) structure. Cases of  human penis  ossification following trauma have been reported, [ 40 ]  and one case was reported of a congenital os penis surgically removed from a 5-year-old boy, who also had other developmental abnormalities, including a cleft scrotum. [ 41 ]   Clellan S. Ford  and  Frank A. Beach  in   Patterns of Sexual Behavior  (1951), p. 30 say, "Both gorillas and chimpanzees possess a penile bone. In the latter species, the os penis is located in the lower part of the organ and measures approximately three-quarters of an inch in length." [ 4 ]  In humans, the rigidity of the  erection  is provided entirely through blood pressure in the  corpora cavernosa . An "artificial baculum" or  penile implant  is sometimes used to treat erectile dysfunction in humans. [ 42 ]


In  The Selfish Gene ,  Richard Dawkins [ 43 ]  proposed honest advertising as the evolutionary explanation for the loss of the baculum. The hypothesis states that if erection failure is a sensitive early warning of ill health (physical or mental), females could have gauged the health of a potential mate based on his ability to achieve erection without the support of a baculum.


The tactile stimulation hypothesis proposes that the loss of the baculum in humans is linked to the female choice for tactile  stimulation : a boneless penis would be more flexible, facilitating a larger range of copulatory positions and whole body movement, giving females greater general physical stimulation. [ 44 ]


The mating system shift hypothesis proposes that the shift towards monogamy as the dominant reproductive strategy may have reduced the intensity of copulatory and post-copulatory sexual selection, and made the baculum obsolete. [ 45 ] [ 46 ]


Humans "evolved a  mating system  in which the male tended to accompany a particular female all the time to try to ensure paternity of her children" [ 16 ] [ better source needed ]  which allows for frequent matings of short duration. Observation suggests that primates with a baculum only infrequently encounter females, but engage in longer periods of  copulation  that the baculum makes possible, thereby maximizing their chances of fathering the female's offspring. Human females exhibit  concealed ovulation , also known as hidden estrus, meaning it is almost impossible to tell when the female is fertile (unless the cervical mucus is examined), [ 47 ]  so frequent matings would be necessary to ensure paternity. [ 16 ] [ 48 ] [ 49 ]


Strengths and weaknesses of these hypotheses were revised in a 2021 study, which also proposed an alternative hypothesis: that conspecific aggression, in combination with the development of self-awareness, may have played a role in the loss. If the presence of a baculum exacerbated the prevalence and severity of penile injuries resulting from blunt trauma to a flaccid penis, increasing ability to foresee the consequences of their actions would also enable hominins to realise that these injuries are a useful tool in male-male competition. This behavioural innovation, planned conspecific aggression with the goal of temporary exclusion of competitors from the breeding pool, would create an environment in which a genetic mutation for a penis without a baculum (or with an unossified baculum) would strongly increase the fitness of the mutant phenotype. Along with the hominin propensity for social learning and cultural transmission, this hypothetical scenario may explain why this phenotype became fixed in all human populations. [ 50 ]


An alternative view is that its loss in humans is an example of  neoteny  during human evolution; late-stage fetal chimpanzees lack a baculum. [ 51 ]