How can hair be white at the tip and brown at the root?

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JoAnna  asked the Naked Scientists:

Dear Dr. Chris,

I love your show, I've been listening to the podcasts for quite some time now. I used to consider myself quite well read, but I've been learning so much from you and your fellow hosts and esteemed guests!

I have a couple of conundrums that you've not quite addressed.

I have very dark hair, and as I age (I turn 38 in January) it's been slowly going gray. So slowly, in fact, that it's not worth the bother of colouring it; I just pluck the white hairs out, which is quite easy due to the contrast.

Sometimes, though, I'll find one where the END is white, and the ROOT has reverted to black! Other times, I'll see a hair that is entirely coppery red, from tip to root.

I looked up a the hair-related questions from previous shows, and while you do address the idea of a slow fade to white...

... You don't mention that these cells can turn back on again, or turn a different color. Am I a freak of nature?

Again, great work! Take pride that you've made me an -even more annoying- competitor during trivia games.


What do you think?


Offline RD

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How can hair be white at the tip and brown at the root?
« Reply #1 on: 17/01/2009 03:28:35 »
Repigmentation can spontaneously occur conditions where pigment is lost (e.g. vitiligo)...

Repigmentation usually occurs around the hair follicles, which is achieved by stimulation and migration of follicular melanocytes.
Spread of pigmentation from the margin of the macules can also occur.

...these findings suggest that the hair follicular melanocytes begin proliferation at the anagen II stage and that the melanocytes proliferate actively at the anagen III stage to repopulate the hair matrix during subsequent hair growth.

Pigmentation of human hair is not uniform along its length...

« Last Edit: 17/01/2009 04:10:58 by RD »