When one grows older, it is not only the hair on the head but that of other parts of the body including the pubis that turns grey. This is because there are cells in the skin and hair pits that produce and supply hair with the black pigment called melanin (melanocytes) that with age die off, leaving hair without pigment (grey).
As we age, the body produces less catalase responsible for breaking down hydrogen peroxide in hair so the hydrogen peroxide builds up and bleaches the hair white (peroxide blonde), the reason greying is associated with age.
Although it may take longer than hair found elsewhere, pubic hair also ultimately turns grey. Men go grey before women, on average, and white people start going grey in their mid-30s, Asians in their late 30s, and Africans in their mid-40s though many Africans are greying earlier nowadays.
Sometimes without even aging, the melanocytes fail to function normally, hence leading to premature greying as early as the 20s. How early one develops grey hair including pubic hair depends on genetics and here the greying is irreversible. Vitamin B-12 deficiency or problems with the pituitary or thyroid gland can cause premature greying that may be stopped and, in a few cases, reversible when the problem is corrected.
Sometimes early pubic hair greying may depend on a combination of factors with, genetics quickening the process for people who are genetically inclined for pubic hair to grey early. Patchy pubic hair greying may result from loss of pigment in the associated skin in a condition called Vitiligo.
Since pubic hair greying is mostly harmless, no treatment is necessary and if one gets cosmetic concerns, he can shave.
Since in a few people the problem may be associated with disease, greying should not be called harmless unless associated diseases are ruled out.
Source: Daily Monitor