Photo:Scotty Reifsnyder

The Scientist: Des Tobin, Professor of Cell Biology and Director of the Centre for Skin Sciences at the University of Bradford in the UK.

The Answer: Sorry, no dice. You can neither slow the onset of graying nor reverse it once it’s happened.

Hair gets its color from melanocytes, pigment-producing cells that live near the base of each hair. As a hair grows, it absorbs pigment, called melanin. The color that results depends on the ratio of eumelanin (which is black/brown) to pheomelanin (red/blonde), and that is determined by genetics, hormones and age. That’s why blonde kids often turn brunette after puberty—and why they go gray as older adults.

Graying happens when your melanocytes begin to produce less melanin, fail to produce melanin altogether or simply die off. Researchers have also found that hydrogen peroxide (a powerful bleaching agent) is produced naturally in the hair follicle, but it's broken down by enzymes. As you age, those enzymes dwindle, letting the hyrogen peroxide bleach hair from the inside out. Most people will have some gray hair by their 50^thbirthdays. Different ethnicities tend to go gray at different ages. Speaking in broad generalities, the average is mid-30s for Caucasians, late 30s for Asians and mid-40s for people of African descent. But some people get salt-and-peppery in their 20s, while others hold onto their hair color until they’re 80.

There are some interesting exceptions to the “gray for good” rule. Certain drugs have been associated with hair darkening, and cancer patients who have undergone scalp radiotherapy have found that the irradiated areas can start producing pigmented hair again. Obviously, these are not workable everyday solutions. In the lab, scientists have been able to restart melanin production in melanocytes that haven’t produced pigment in a long time, so a treatment for gray hair at some point in the future isn’t out of the question. But it’s not exactly on the horizon, either.

Thank You:You Beauty