Rebecca Watson, age 8, of Chester, Penn., for her question:

WHAT CAUSES AN ITCH?

An itch is a sensation caused by irritation of particular nerves in the skin.

Nerve fibers have special endings that are tiny organs able to receive messages. Some nerve endings receive pressure sensations, some receive temperature and some receive pain. Stimulation of pain nerves in the skin sometimes results in itching.

Many different causes may produce itching. A common cause is some chemical that touches the skin and irritates it, such as poison oak or ivy.

An allergy may release chemicals that make the skin swell and itch. This condition is hives. Another condition, called the itch, is caused by a mite that burrows into the skin.

Itching often results from athlete's foot, which occurs on the toes and feet. Cool, moist applications soothe itching.