Hair loss afflicts millions of people—and not just men, though their hair loss is often the most noticeable. Most women, too, experience some degree of hair loss as they grow older.
Hair is not living tissue like skin but is composed of a protein called keratin, which is also the building block of fingernails and toenails. Each hair grows from a root enclosed by a follicle, a small pocket in the skin, which is nourished by blood vessels. Hair grows according to a genetic program (hormones also are involved), about half an inch a month; each hair grows for two to six years.
Part of your hair is growing and part is resting at any given moment. After the rest period, the hair falls out. It’s normal to lose 50 to 100 hairs a day (not many out of the 100,000 in the average youthful head). When a hair falls out, a new one presumably grows in, but the catch comes when it doesn’t— when more falls out than grows back in. Genetic baldness is caused by the body’s failure to produce new hairs. Nearly two thirds of men develop some form of balding.
By far the most common form of hair loss is androgenetic alopecia, usually called male-pattern baldness. (Alopecia is the medical term for hair loss.) It is typified by the receding hairline that eventually turns into a bald pate (sometimes with very fine, thin hairs replacing the original growth). By age 50, half of all men of European origin will experience this kind of hair loss, which can begin as early as age 20. Several other genetic groups—some Asians, some Africans and African Americans and Native Americans—seldom or never get bald in this manner. Though the exact process that shuts down the hair follicles has yet to be explained, the male hormone testosterone plays a role.
What causes it? Hereditary pattern baldness is determined by our genes and hormones. Sudden, dramatic hair loss, however, can have many causes. In both men and women, severe emotional stress, fad diets if pursued to the point of malnutrition, thyroid disorders, anemia and various drugs and medications (particularly therapy for cancer) can cause hair loss. Large doses of vitamin A also may cause the problem.
Hair loss caused by constantly wearing tight-fitting wigs or hats is called friction alopecia. Traction alopecia is hair loss caused by pulling hair too tight in ponytails or braids, so that it falls out. In most of these cases, hair begins to grow again once the underlying problem is corrected or corrects itself.
More serious is alopecia areata (“area baldness”), which causes loss of hair in patches and is thought to be an autoimmune disorder. It can proceed to complete hair loss and affects about five million people in the United States, male and female. This condition can sometimes be treated successfully, and anyone who suffers from it should see a dermatologist. In many cases, it simply goes away by itself and new hair grows back in.
It’s impossible to prevent male-pattern baldness, and in most people the baldness will almost always become more noticeable with age. For hair loss caused by illness, medication, radiation therapy or hormonal fluctuations, hair will usually grow back when the condition has improved or treatment has ended.