What Causes Human Hair to Turn Gray?

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If you're concerned about going grey, the bad news is that your risk of seeing strands of silver increases by up to 20 percent every 10 years after age 30, states the Library of Congress website. While there are extrinsic factors that can cause you to go grey sooner than you anticipated, the most common reason your hair loses its natural color is closely linked to your genes and the intrinsic aging process.


The color of your hair would be naturally transparent if it weren't for melanin, the pigment that gives it color. There are two types of pigments that combine to give our hair its natural shade, says the Library of Congress: eumelanin and phaeomelanin, which produce dark and light hair color, respectively. As a strand of hair grows, special cells called melanocytes delivers pigment to the hair. Once melanocytes die, this causes a reduction in the amount of pigment delivered to the hair. The hair turns grey and then eventually white when all pigment is depleted.


Your genetic makeup is an intrinsic factor that determine when your hair goes grey, as well as how rapidly your hair will lose its color. Each melanocyte has a type of pre-programmed time clock that dooms it to expire at a certain point in your life. The Nemours Foundation points out that some people start getting premature grey hairs when they're in high school or college. Typically, you'll begin to see silver hairs in your hair at the same time your parents or grandparents did.


Genetics and aging are inextricably linked when it comes to grey hair. As noted above, your genes influence the age at which you first see grey hair. The National Institutes of Health states that grey hair generally starts in your 30s, beginning at the temples and then moving into the top of the scalp. Over time, the hair looks less grey as more melanocytes die, and eventually it turns white. Body hair turns grey at a slower rate than the hair on your head, and in some cases, it doesn't lose any pigment at all.

Other Factors

Other extrinsic factors can contribute to grey hair but do not necessarily cause it; the climate in which you live, pollution, toxins and exposure to chemicals can hasten grey hair along, says the Library of Congress. Other factors may cause hair to grey before its time, according to the consumer website GreyHairLoss.com. These include stress, smoking and health certain medical conditions, such as vitiligo, thyroid problems, vitamin B deficiency and anemia.