Gray hair is hair that has a color somewhere between black and white.
OK, you probably want to know why we get gray hair. Hair gets its color from the chemical melanin, the same stuff that makes people's skin dark either genetically, or from tanning. This chemical is produced by melanocytes, which have trouble producing melanin as you get older, which results in the development of liver spots on the skin, and graying of your hair. When this happens depends mostly on your genes. Albinos have white hair because they can't produce melanin.
Despite superstition, people cannot get gray hair from a traumatic experience. However, premature grayness can be caused by vitiligo, a disease which disrupts the production of melanin. New research on the affliction has led scientists to believe that vitiligo, as well as normal graying, may be a result of hydrogen peroxide in our skin. People with vitiligo have very low levels of catalase, a chemical that breaks down hydrogen peroxide: hair follicles naturally produce hydrogen peroxide, which may eventually build up limiting the production of melanin. It's hoped that one day this will be controlled, letting us retain our hair color and perhaps treat melanoma, a type of skin cancer made up of melanocytes.
There is no connection between graying and health, although the darker your skin is naturally, the longer it will take before the process starts: Caucasians generally start graying the earliest at age 35, followed by Asians, and finally Africans. Currently, there is no scientific explanation for salt and pepper hair, in which some hairs turn gray and others do not.
Posted 3953 day ago