9 Things You Didn't Know About Grey Hair

While some women proudly sport a silver mane, many others face the arrival of new gray hairs with dread. The good news: Scientists are hard at work on how to prevent them. So what do researchers know that you don't?

1. Normal ageing is the biggest culprit.
   Okay, no surprise here. Dermatologists call this the 50-50-50 rule. "Fifty percent of the population has about 50% gray hair at age 50," says Dr. Anthony Oro, professor of dermatology at Stanford University. And like skin, hair changes its texture with age, says Dr. Heather Woolery Lloyd, director of ethnic skin care at the University of Miami School of Medicine.
2. Your ethnicity makes a difference.
   Caucasians tend to go gray earlier - and redheads earliest of all. Then Asians. Then African-Americans. Scientists haven't figured out why yet.
3. Stress seems to play a role.
   "Stress won't cause you to go grey directly," says Dr. Roopal Kundu, associate professor in dermatology at Northwestern University's Feinberg School of Medicine. "But stress is implicated in a lot of skin and hair issues." During an illness, for example, people can shed hair rapidly. And hair you lose after a stressful event - like getting chemotherapy - may grow back a different colour.
4. Your lifestyle makes a difference.
   Smoking, for example, stresses your skin and hair. "Low vitamin B12 levels are notorious for causing loss of hair pigment," says Dr. Karthik Krishnamurthy, director of the Dermatology Center's Cosmetic Clinic at Montefiore Medical Center in the Bronx, New York. Try eating foods such as liver and carrots, recommends Dr. Wilma Bergfeld, a senior dermatologist at the Cleveland Clinic. Foods packed with certain vitamins, nutrients and antioxidants may help protect cells against toxins and help prevent heart disease, cancer, and other ailments (and perhaps grey hair!).
5. Hair and its colour are separate things.
   Hair stem cells make hair, and pigment-forming stem cells make pigment. Typically they work together, but either can wear out, sometimes prematurely. Researchers are trying to figure out if a medicine, or something you could put in your scalp, could slow the greying process. (Hair dye simply coats your hair in colour but doesn't alter its structure.)
6. Your hair basically bleaches itself.
   You may be familiar with hydrogen peroxide as a way to go blonde, but it's also the way we go grey. According to a 2009 study published by the Federation of American Societies for Experimental Biology, hydrogen peroxide naturally occurs in our hair follicles, and as we get older, it builds up. This build-up blocks the production of melanin, a.k.a. our hair's pigment.
7. Your hair doesn't turn grey - it grows that way.
   A single hair grows for one to three years, then you shed it - and grow a new one. As you age, your new hairs are more likely to be white. "Every time the hair regenerates, you have to re-form these pigment-forming cells, and they wear out," says Oro.
8. Grey hair isn't more coarse than coloured hair.
   Gray hair is actually finer than coloured hair, but it may seem drier because our scalps produce less oil as we get older. Another reason it could seem more rough? "Your hair may also 'feel' coarser if you pull out your first few grey hairs," says Philip Kingsley trichologist Glenn Lyons. "This is because constant pulling-out of hair can distort your follicles, resulting in more crinkly hair."
9. Grey hair can be resistant to colour.
   If you opt to colour your hair, you may find that it's more stubborn about taking colour than before you started going grey. "Some grey can be resistant to hair colour," say the experts at Madison Reed. "If this is true for you, consider dropping down a colour level or using something darker on your roots to deliver even more coverage."