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Human beings have many variations in hair color and texture.
Hair color is the result of pigmentation due to the presence of the chemicals of melanin. In general, the more melanin, the darker the hair color.
In general, the color of children's and adults' hair varies from pale yellow to deep black. The ethnic distribution of colors has historically varied by geographic area. For example, deep brown and black prevail in Asia, North Africa, and Mediterranean Europe, and even darker shades occur in tropical Africa and Central America; lighter brown is more common in central Europe, yellow/blond in northern Europe, and reddish in the British Isles.
However, considerable differences in hair color and texture exist between individuals of similar ethnicity, and immigration and global travel have greatly increased the diversity of hair characteristics in many countries.
Names for human hair colors include brun[ette], brown, black, raven, midnight, blond[e], sandy blond[e], dirty blond[e], strawberry blond[e], platinum blond[e], flaxen, auburn, red, russet, ginger, and grey, silver, salt and pepper, and white.
People also change their hair color to colors that aren't their natural ones.
Effects of aging on hair color A change in hair color also typically occurs naturally as people age, usually turning their hair from its usual color to gray at first, and then white. The change is caused by the gradual decrease of pigmentation that occurs when melanin ceases to be produced in the hair root, and new hairs grow in without pigment. It is common as people age (More than 40% of Americans have some gray hair by their fortieth birthday.), but can occur as early as the teens and twenties for some. The determination of when someone begins graying, whether it comes with aging or prematurely, seems to be almost entirely based on genetics.
There are no special diets, nutritional supplements, vitamins, or proteins that have been proven to slow, stop, or in any way affect the graying process, although many have been marketed over the years.
Many people use hair dye to disguise the amount of gray in their hair.
A 1996 British Medical Journal study conducted by J.G. Mosley, MD found that smoking may cause premature graying. Smokers were found to be four times more likely to begin graying prematurely, compared to nonsmokers in the study. [1] (http://bmj.bmjjournals.com/cgi/content/full/313/7072/1616)
Medical conditions affecting hair color Albinism is a genetic abnormality where no pigment is found in human hair or eyes, making the eyes a pale blue and the hair white.
Vitiligo is a patchy loss of hair and skin color that may occur as the result of an auto-immune disease.
Werner syndrome and pernicious anemia can also cause premature graying.
See also
External links and references - Mechanisms of Hair Graying: Incomplete Melanocyte Stem Cell Maintenance in the Niche (http://www.sciencemag.org/cgi/content/abstract/307/5710/720)
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