Why does the hair turn gray?

This week's viewer question comes from Abu Ali A. in Egypt.

Transcript

00:00 Why does our hair turn gray?

00:03 Actually gray hairs are not really gray at all.

00:08 They're white. But layered with surrounding hair of different colors,

00:11 the white hairs can make the hair as a whole appear gray.

00:15 The pigment melanin is responsible for hair color.

00:19 In humans, that's also the pigment that determines eye and skin color.

00:23 The melanin in the hair forms in its roots in particular cells, the melanocytes.

00:31 They produce two different chemical types of the pigment,

00:35 black-brown eumelanin and pheomelanin, which is reddish-yellow.

00:40 The amounts and mixture of these two compounds determines your hair color.

00:44 The older you get, though, the less melanins the melanocytes produce.

00:48 Instead, colorless bubbles of oxygen accumulate in the hair,

00:53 making it look white.

00:58 Exactly when the first white hairs appear varies from person to person.

01:02 Most people start to find them between the ages of 30 and 50.

01:06 But it comes down to your genes.

01:09 If parents go gray when still young, the trait can be passed on to their children.

01:15 But your hair can't turn gray overnight, as some legends claim.

01:21 The French queen Marie Antoinette is said to have gone gray the night before she was

01:26 beheaded in 1793.

01:31 But graying is, by its nature, a gradual process.

01:35 Once a hair grows past the scalp, it no longer changes color.

01:39 And since even white hair only grows between 1 and 1 and 1/2 centimeters a

01:43 month, there's at least a little time to get used to the new look.

01:48 (upbeat music)