The ABCs of Premature Graying

American Idol winner Taylor Hicks sports a gray thatch and he's only 29. CNN's Anderson Cooper says he started to see salt mixed in with the pepper at age 20. Phil Donohue has used his striking white hair for decades to create an aura of eminence.

But take notice -- these are all men. Women, with the possible exception of household hinter Heloise and her long white mane, usually don't flaunt the early gray look.

Why do some people go gray early? And does it have any health implications?

How Hair Works

Hair grows in stages, with a certain percentage of hair either growing or resting at any one time. The hair follicles -- the little bags under the skin where hair is formed out of skin -- also contain pigment called melanin.

When the body stops producing pigments, the hair becomes colorless, turning white. Mixed with darker hair, this produces a look most commonly associated with "gray." An actual gray hair may be a result of pigment dilution.

Why Start This Early?

"Premature graying is genetically determined for the most part," David Bank, MD, tells WebMD. Bank is director of the Center for Dermatology, Cosmetic, and Laser Surgery in Mount Kisco, N.Y. "Graying is natural. We all do it eventually."

When more than half the hair is white by age 40, though, this is considered "premature."

Bank also points out that head hair grows more actively than body hair. So the head can go gray while other hairy parts remain your normal color. Correction: Your former color.

Basically, Bank says, if you look around your family and see a lot of gray, you may be headed in that direction.

What About Turning White Overnight?

A good scare, legend has it, can turn hair white overnight. Martyr Thomas More and the notorious Marie Antoinette supposedly went "white" the night before their executions.

What about Cooper? His new book, just out, titled A Memoir of War, Disasters, and Survival, recounts many harrowing adventures. Could his exploits have turned him white?

Of course, existing hair cannot "turn" any color because the part above the skin is already whatever color it is. One explanation for this "white overnight phenomenon," is that the dark hairs suddenly fall victim to an autoimmune condition called alopecia areata, which can cause dark hairs to fall out overnight -- leaving the white ones.

Bank adds that the dark hair can fall out in quite large quantities in a short period of time and you might not notice. "I know that sounds weird," he says, "but some goes down the drain. You may not notice."

He also points out that going gray does not mean that your body's aging process has sped up. You aren't suddenly going to lose function in other areas.