Hair Color

Hair color is the result of pigmentation due to the presence of the chemicals eumelanin and pheomelanin. In general, the more melanin present, the darker the hair color; the less melanin, the lighter the hair color. Black hair predominates outside of Europe. more...

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A person's hair color may also change over time and may be more than one color at a time. Considerable differences in color and texture exist between individuals of similar ethnicity, and immigration and global travel have greatly increased the diversity of hair characteristics among many countries.

Pigment

There are two types (three subtypes) of pigment that give hair its color: Eumelanin & Pheomelanin, Eumelanin is black and brown while Pheomelanin is red.

The amount of eumelanin in hair determines the darkness of its color. A low concentration of brown eumelanin in the hair will make it blonde, whereas more brown eumelanin will give it a brown color. Much higher amounts of black eumelanin will result in black hair, and a low concentration of black eumelanin in the hair will make it gray.

All humans have pheomelanin in their hair. Pheomelanin is more chemically stable than black eumelanin, but less chemically stable than brown eumelanin, so it breaks down more slowly when oxidized. This is the reason bleach will cause darker hair to turn reddish brown during the artificial coloring process. As the pheomelanin continues to break down, the hair will gradually become orange and, later, yellow and then white.

Effects of aging on hair color

See also: Gray hair

A change in hair color typically occurs naturally as people age, usually turning their hair from its natural color to gray and then to white. More than 40 percent of Americans have some gray hair by their fortieth birthday, but white hairs can appear as early as childhood. The age at which graying begins seems to be almost entirely based on genetics. Sometimes people are born with gray hair because it is passed down genetically. Some people use hair dye to disguise the amount of gray in their hair.

The change in hair color is caused by the gradual decrease of pigmentation that occurs when melanin ceases to produced in the hair root and new hairs grow in without pigment. Two genes appear to be responsible for the process of graying, Bcl2 and Mitf. The stem cells at the base of hair follicles are responsible for producing melanocytes, the cells that produce and store pigment in hair and skin. The death of the melanocyte stem cells causes the onset of graying.

Artificial factors affecting hair color

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.

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