Hair colour
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Human beings have many variations in hair colour and texture.
Hair colour is the result of pigmentation due to the presence of the chemicals of melanin. In general, the more melanin, the darker the hair colour.
In general, the colour 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 the Middle East, 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 colour 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 colours 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 colour to colours that aren't their natural ones.
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Effects of aging on hair colour
A change in hair colour also typically occurs naturally as people age, usually turning their hair from its usual colour 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 grey 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 tobacco 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 colour
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 colour that may occur as the result of an auto-immune disease.
Werner syndrome and pernicious anemia can also cause premature graying.
Archaeological Hair
The colour of the hair of mummies or buried people can change over large time periods. Hair contains a mixture of black-brown eumelanin and red-yellow phaeomelanin. Phaeomelanin is much more stable than eumelanin, so that the phaeomelanin in the hair is better preserved and enhanced over time than the eumelanin. The colour of hair changes faster under extreme conditions. It changes however more slowly under dry oxidising conditions (such as in burials in sand) than under wet reducing conditions (such as burials in wood and plaster coffins).
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)
- Archaeological Hair (http://www.archaeology.org/interactive/hierakonpolis/field/hair.html)