Why do blond kids go brown?
Originally Published: January 30, 2004
Why are some people born blonde but turn brunette as they get older?
People learn in school that hair color, like eye color, is determined by genes. Many think that everyone has one hair color gene, but that's not the case. Each person has several genes that determine his or her hair color, and different genes are active at different stages in that individual's life, resulting in changes in hair color. Our genes determine the level of pigmentation present in our hair (not to mention our eyes and skin).
When it comes to hair color, there are two types of pigment (melanin), called eumelanins and pheomelanins. Dark brown or black hair is a result of eumelanins, and pheomelanins are responsible for blond or red hair. The combination of these two pigments creates each individual's unique hair color, and the level of pigmentation changes depending on the genes that are active at that point in a person's life. Blond hair can turn brown, brown hair can turn darker brown, and red hair can turn auburn. And some people's hair even stays the same color.
Of course, most people also experience a change in hair color later in life, when their hair starts to turn grey or white as part of the aging process. This results not from a change in activity of specific genes, but the slowing down or ceasing of production of the enzyme that creates pigment.