Anne Thayer, age 13, of Richmond, Va., for her question:

WHAT IS DANDRUFF?

One of the characteristics of mammals is that they all have hair. Hair is actually a protector of the body, and it grows from special places in the skin. Small glands at each hair provide oil to keep it from becoming dry and cracking. And sometimes the skin near the hair produces a buildup of material that comes off in small scales called dandruff.

Dandruff is usually more annoying than serious. Flaky scales that fall from the head to the shoulder car. be a problem.  Dandruff is called seborrheic dermatitis of the scalp.

It is actually an excessive supply of sebum, the oily secretions from the sebaceous glands of the skin. The result is greasy scaling of the skin surface.

Although dandruff usually first appears on the scalp and in most cases remains only there, it is possible for it to spread to the forehead, eyebrows, eyelids, parts of the nose and the area behind the ears. In addition, it can be found on the chest or under the armpits and elsewhere, particularly where there is hair on the body and sebaceous glands are numerous.

Did you know that infants can develop dandruff? There's a type called infantile seborrheic dermatitis that is sometimes found on a baby during the first three months of its life. Starting with dandruff like symptoms on the scalp, it spreads over other parts of the baby's body. It disappears in a short time and doesn't require any special treatment.

With some teen alters, but more likely with adults, dandruff is widespread. it may last only a few weeks or for longer periods up to a lifetime.

We do not know exactly what causes dandruff. Fungal organisms are often found in the flaking skin, but these may be secondary invasions of the skin, made easier by the seborrheic condition.

Dandruff of the scalp is controlled by washing the hair with nonalkaline soaps or shampoos. Special preparations using sulfur and tar are also used in shampooing.

Some doctors suggest special diets for patients with seborrheic dermatitis, similar to those suggested for acne patients.  As in acne, a disease that also involves problems of the sebaceous glands, there seems to be a relation between hormones and the onset of dandruff. The problem also seems to worsen in winter and during periods of stress or fatigue.