Hair Color

Pigmentation

color is perhaps the most obvious characteristic of hair, but as far as we know it has no biological function in humans. It does not protect the hair from the harmful effects of sunlight (although hair itself protects the scalp, of course).
    As we have seen, the color of hair is due to the presence in the cortex of granules of a pigment called melanin, which is formed in special pigment-producing cells (melanocytes) in the hair bulb during the growing phase (anagen) of each hair. The melanin granules lie along the amino acid chains of the proteins, looking under the microscope rather like a string of pearls.
    Melanin is found in two forms. Eumelanin is the dark pigment which predominates in black and brunette hair. Phaeomelanin is a lighter pigment, which is found in red and blond hair. Many people's hair contains a mixture of the two: the more eumelanin there is in the mixture, the darker is the hair. The mixture (and the shade) varies not only from one person to another, but also across one person's head. The combination of pigments in the mixture is determined by the individual's genes. Differences between dark-haired people are due to differences in the overall quantities of melanins in their hair.
    Eumelanin granules are oval (elliptical) in shape, fairly uniform in their make-up and quite hard, with sharply defined edges. Phaeomelanin granules are smaller, partly oval and partly rod-shaped.
    The range of colors produced by melanins is limited to shades of yellow, brown, red and black. Grey hairs contain only a few melanin granules, spread out through the hair. White hairs contain no melanin at all: their whiteness is an optical effect, due to the way they reflect the light. Surprisingly, however, unpigmented hairs look yellow (the 'color' of keratin) when they first grow, and only later turn white.

Melanin granules in the cortex of a hair

Genetic differences

Ethnic differences in hair color are as obvious as are differences in hair type. Most people in the world have dark hair, though in northern Europe blond hair is the most common. Curiously, however, people with blond hair and/or blue eyes are found even in North Africa and the Middle East.