sometimes i find a hair which is white a the tip and black again at the roots, why?
816810
time. you are getting old.
469294
Hair is an interesting biological structure. What we usually think of as 'hair' is really just the part we see... that's the hair shaft, which contains pigment (a chemical that gives color to things). There is also a hair follicle, which is a multi-cellular structure inside the skin of our scalp that creates the hair strand (making it grow), and also is responsible for the pigmentation. Some of the cells in the follicle make the chemical melanin, which is a skin and hair pigment in many species on our planet. \n\nHair turns grey when the pigment cells in the hair follicle stop making melanin. When this happens due to aging, it's mostly under the control of the genes we inherit. Long periods of constant stress may also contribute, but a big shock won't turn hair grey overnight.
393736
hair, because hair does not live once out of the follicle.
524267
Your hair is coloured by melanin (pigment cells) and as you get older the melanin in our hair follicles gradually die. When there are fewer pigment cells, your hair becomes more transparent and looks grey/white.
220769
I'm sure you've seen people with very dull-looking hair.  It's probably because they've used harsh chemicals on it.  A good example is a bleached blonde.  A lot of the cuticle has been damaged, so there is no natural shine.  \n\nAlso, split ends are not part of the "outside" healthy appearance of hair.
589709
I had the same problem, but it went away.  The strangest thing was that when my hair grew back in, it was much darker and much curlier than it had been before.  That went away, too, though, after it grew out for a few months.
616599
buy some hair dye early greying happens to some people
25922
Good question.  I believe that it's hereditary.  My Dad was completely white before he was 18.  I started to get white hair at the temples when I was 13.  My two daughters had a few white hairs in their teens.
991573
It probably has to do with the denaturing of proteins within the hair. Check out the website it might answer your question more thoroughly.
845816
Sometimes, "premature graying" (what you're referring to) happens/begins to happen as early as in the 20's and 30's...some people start having it happen later. It's a heredity and genetic thing. Hair color is the only thing I know that can make it LOOK BETTER--nothing, as of this moment, can stop it. The pigment (the thing that determines hair color) is gone in those spaces where the gray or white are. Don't freak out.
752116
It is normal to have few strands.\n\nIf it is a lots of hair see a doctor he/she can check the level of Harmon and let you know.
583867
In black stripes, cells surrounding hairs have a high rate of melanin production. In white stripes, melanin production is blocked genetically so hairs in that zone are white. The mechanism is the same as in cats, for example.
1054652
Not all of us get back hair!
378580
Did you ever notice the diameter of an Asian person's hair?  It is thicker than a Causcasians.  I am sure the sheer thickness has something to do with it.
216454
For about 2 years now, I have been dying my hair unnatural colors. October was the last time that I bleached my hair, so the portion that I can dye is growing out. My hair is currently its natural color (black with a few errant white hairs) at the roots and green everywhere else.\n\nMy hair colors during this period of funky colors have included:\npurple\nelectric blue with atomic pink bangs\natomic pink \niguana green\nflame colored - a mix of blood red and bright as f*$k yellow...sort of looked like the Heat Miser from the Christmas cartoon "The Year Without a Santa Claus".\nblood red\nplatinum blonde\npillar box red
740032
I'm not for sure but I think it is the way that it grows or maybe the fine little hairs that grow on them. This site might help you more than I could.
1172727
The root of every strand of hair is surrounded by a tube of tissue under the skin that is called the hair follicle (say: fah-lih-kul). Each hair follicle contains a certain number of pigment cells. These pigment cells continuously produce a chemical called melanin (say: meh-luh-nin) that gives the growing shaft of hair its color of brown, blonde, red, and anything in between. \n\nMelanin is the same stuff that makes our skin's color fair or darker. It also helps determine whether a person will burn or tan in the sun. The dark or light color of someone's hair depends on how much melanin each hair contains.\n\nAs we get older, the pigment cells in our hair follicles gradually die. When there are fewer pigment cells in a hair follicle, that strand of hair will no longer contain as much melanin and will become a more transparent color - like gray, silver, or white - as it grows. As people continue to get older, fewer pigment cells will be around to produce melanin. Eventually, the hair will look completely gray. \n\nPeople can get gray hair at any age. Some people go gray at a young age - as early as when they are in high school or college - whereas others may be in their 30s or 40s before they see that first gray hair. How early we get gray hair is determined by our genes. This means that most of us will start having gray hairs around the same age that our parents or grandparents first did. \n\nGray hair is more noticeable in people with darker hair because it stands out, but people with naturally lighter hair are just as likely to go gray. From the time a person notices a few gray hairs, it may take more than 10 years for all of that person's hair to turn gray. \n\nSome people think that a big shock or trauma can turn a person's hair white or gray overnight, but scientists don't really believe that this happens. Just in case, try not to freak out your parents too much. You don't want to be blamed for any of their gray hairs!