Answer:

"Premature graying of the hair is usually just a manifestation of the aging process and, in the vast majority, is nothing more than a cosmetic blight," says Jerome Z. Litt, MD, an assistant clinical professor of dermatology at Case Western University in Cleveland. The graying of hair is caused by a decrease in pigmentation -- color -- in the hairs. While everyone succumbs to graying at some point, premature graying is defined as "the onset of graying before the age of 20 in Caucasians and before the age of 30 in blacks," says Litt.

Most people who go gray early have nothing more to worry about than their appearance. But for a few, premature graying may be a sign of disease. "Premature graying can occur with a number of conditions, including hyperthyroidism, hypothyroidism, and pernicious anemia," says Litt.

Pernicious anemia is a rare type of anemia in which the blood cannot absorb vitamin B-12, which is necessary for the production of red blood cells. Pernicious anemia can be diagnosed through a blood test and is simply treated with vitamin B-12 injections. "Other symptoms will be present besides premature graying in a person with pernicious anemia," assures Litt, including fatigue, shortness of breath, and possibly chest pains.

Certain drugs, herbs, and supplements -- including vitamin E and echinacea -- are also known to cause graying. In addition, smoking has been linked to early graying. A study published in the December 21, 1996 issue of the British Medical Journal suggested a connection between smoking and gray hair (as well as between smoking and male baldness). The researchers were not, however, able to determine a direct cause-and-effect relationship.

In general, however, the appearance of a gray hair or two, or more, is simply a sign that you're aging normally. "Remember, one rose does not a summer make," quips Litt. In other words, you are more than just your hair, gray or not.