Why is ultraviolet light damaging to the skin?
337914
Ultraviolet light is able penetrate through the outer cells of our integument (skin). Doing this exposes the DNA to potential damage. \n\nThe damage that is proposed to be caused by the UV light has changed in recent years. It used to be thought that UV light caused the base pairs to fuse (a base pair refers to the fact that complimentary bases from opposite strands hydrogen bond with one another -- Adenine (A) bonds with Thymine (T); Guanine (G) pairs with Cytosines (C). Howver, it's been recently shown that as sunlight warms our skin, UV photons are absorbed by the bases, causing their electrons to vibrate. These high-energy vibrations nudge the atoms in the bases around. If all goes well, the DNA returns to normal after the energy wave passes. But some of the time, the atoms don't return to their original positions, and new chemical bonds are formed.\n\nScientists know that such accidental bonds create "photolesions" - injuries that prevent DNA from replicating properly. The details of the process aren't fully understood, but studies suggest that photolesions cause genetic mutations that lead to diseases such as sun damage as well as cancer.\n\nBecause skin cells need to replicate often this damage can either slow them down causing skin damage or speed them up to the point of becoming cancerous.
568270
The most common causes of skin cancer are:\nExposure to ultraviolet radiation from the sun between 10:00 a.m. and 3:00 p.m. and exposure at high altitudes. \nDamage to the DNA of melanocytes from exposure to the sun and its UV light radiation is the single most important factor in the cause of melanoma. \nTanning salons also expose your body to UV radiation and increase your risk of developing melanoma. \nThe depletion of the ozone layer may be significantly affecting the incidence of melanoma. It is estimated that there is a 1% increase in melanoma with each percentage decrease in the ozone layer. \nFamily history of melanoma. \nAtypical moles. \nAn impaired immune system, especially if you have had an organ transplant, leukemia, or lymphoma.
432601
the UV waves cause heterolytic fission of chemical bonds creating "radicals" which are very reactive species.  They will react with pretty much anything.  The UV radiation is therefore breaking down the skin and the colour molecules in paint and clothes, making them look like they are losing their colour.  The purpose of sun-tan lotion is not only to stop the UV radiation getting to your skin, but also to mop up all the free-radicals formed before they do any damage.  Skin cancer is caused by this process.  You are essentially changing the structure of the skin.
270665
C\n\n\nOzone layer is responsible to inhibit UV radiation from Sun to reach earth. Once Ozone layer vanishes, UV radiations are free to reach earth which may cause skin cancer and other diseases.
758324
being black does not mean you are sun immune,you must use the sunscreen to avoid photodamage to the skin caused by ultra-violet rays..
1000863
Too many to list I think, and not being a doctor of chemist I wouldn't know - but I think there are some anti-depressants that may cause the skin to be UV sensitive as I seem to remember someone on various anti-nuts-o medications that effected their sensitivity to the sun.
1168385
Because of their skin color. I know that everyone needs to put on some sun screen. Just because your skin is dark doesn't mean you are protected form UV rays.
764200
At least one scientific study ( http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowPDF&ProduktNr=224197&Ausgabe=227414&ArtikelNr=46495 ) shows that result. They exposed skin to UV rays and observed a rise in serotonin. "This is due to photoinhibition of enzymes converting serotonin to melatonin.", which means that the serotonin that would otherwise be converted to melatonin stays as serotonin. I think it would be best to read the article.
986235
UV light will destroy it
363967
No reason you shouldn't. Sunlight helps activate Vit. D. The only reason you would is if you are taking some medication that can cause problems when you expose yourself to UV waves. There are to many for me to mention here. If you have a list though I would be glad to tell you.
947451
I am not sure, but melanin the coloured pigment which protect DNA from harm such as harmful UV rays.  Darker people in hot counries cope better with sunshine.  Although some of tanning may be due to damage, it may be a result of transcription of the protein melanin
505387
Ozone (O3) reflects/scatters ultraviolet radiation back into space.  However, if it is depeleted, this radiation makes it past the atmosphere and down to the surface.  The amount of shorter wavelength (higher energy) radiation passing through the atmosphere would increase, causing higher mortality rates from skin related ailments and can also destroy plant tissue.  Also, this radiation would heat the earth more since it carries more energy with it.  This is not usually a problem, since this thermal radiation currently passes back into space.  However, with pollution clouds/dust being more prominent, it would reflect the thermal radiation back down to earth's surface, driving the temperature up even more.
1068342
The Ozone screen most of the hamful UV (mostly UV-B) away from reaching the earth....\n\nTherefore, Ozone depletion will allow more harmful UV reaching the earth, and the harmful UV (UV-B) will cause skin cancer and other eye problems in human in prolong explosure.
354531
Sometimes too much sun can have the opposite effect on skin.  Skin pigment cells called melanocytes are over-stimulated and essentially "burn out."  This usually presents as pinpoint light areas and is called guttate hypomelanosis. \nHere is a web site with photos.\nhttp://dermnetnz.org/colour/guttate-hypomelanosis.html
831677
It stings much like you scaled yourself with very hot water.  It really is a dumb idea to allow yourself to get a sunburn. Very light skinned people really should avoid the sun altogether.   Since my family came from the Artic Circle, we are especially vulnerable.
989150
It's because of evolution, yes. When people are exposed to higher levels of ultraviolet light, extra melanin in the skin will reduce the risk of skin cancer and will therefore be a survival advantage, so natural selection will favour dark-skinned individuals with the genes for producing extra melanin. Individuals with these genes are more likely to survive to childbearing age and will be more likely to pass on the genes. In colder climates, extra melanin does not affect the chances of survival as much so it is not selected for, though characteristics such as extra body hair and fat may be selected for.
759597
No- not really.  Especially not for naturally fair people.  The American Cancer Society research I've seen generally contributes most cancers of the skin to exposure to UV at younger ages.  A self tanner is generally the best way to go.  Lancome and Neutrogena make great ones.