Katy Hatcher age 14, of Henderson, Nev., for his question:

WHY DOES A CALLUS OR CORN FORM?

A callus is a hardening and thickening of the skin. It often forms on the feet and hands. Poorly fitted shoes can cause calluses on the heels and soles of the feet. A corn is a special kind of callus, usually found on the feet.

Hand calluses result from prolonged rubbing on some hard object.

Many calluses can be treated by soaking them in water and applying a salicylic acid solution or other softening preparation.

A corn is a hard, shiny thickening of the epidermis or outer layer of skin. This thick growth presses on the dermis or deeper skin layer and causes it to become thin and tender.

Pressure and friction cause corns. Therefore, corns often develop over the joints of the toes of persons who wear shoes that do not fit properly. A soft corn is one located between the toes.

Corn plasters do not cure corns. To cure them, a person must remove the thing that causes it to form. But he may use plasters to relieve pain. Because of the danger of infection, paring corns with sharp instruments should be done only by a doctor.