How does Hair Turn
When the bulbar melanogenic melanocytes stop producing melanins, hair is gray, eventually becoming white, when the hair shaft is just keratin. Keratin is the stuff your fingernails are made of, and there you can see keratin is translucent and colorless. The keratin layer in the hair cuticle is far thinner than your fingernail, so it is transparent. Hair with no melanin particles in the hair cortex is completely white. Hair with a few melanin particles in the hair cortex is still gray.
White hair may grow faster than pigmented hair! In non-balding individuals, white hair grows most rapidly among people in their 60's and 70's (Pelni et al., 1969). White beard hairs often grow at up to four times the rate of adjacent pigmented hair (Nagl, 1995). For some aging people, nostril hairs fall into this delightful category. For others, eyebrows and ear hairs are similarly invigorated.
If you want to dye your beard and nostril hairs with henna, you'll have to touch up the roots frequently!
D.J. Tobin, R. Paus
Graying: gerontobiology of the hair follicle pigmentary unit
Department of Biomedical Sciences, University of Bradford, Bradford, West Yorkshire BD7 1DP, UK
Department of Dermatology, University Hospital Eppendorf, Hamburg, Germany
Experimental Gerontology 36 (2001) 29-54
Pelfni, C., Cerimele, D., Pisanu, G., 1969.
Aging of the skin and hair growth in man.
R.L. (Eds.). Advances in Biology of the Skin – Hair Growth. Pergamon Press, New York, pp. 153-160.
Nagl, W., 1995.
Different growth rates of pigmented and white hair in the beard: differentiation vs. proliferation
Br. J. Dermatol. 132, 94-97.
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