Lee Ann Wood, age 11, of Shreveport, La., for her question:

WHAT CAUSES A STY?

A sty is an infection of one of the glands of an eyelid, usually around an eyelash. The inflammation, which resembles a small boil, is usually caused by a staphylococcus bacteria.

The germs enter the root of the eyelash, grow there and form pus. Some experts believe that eyestrain is an indirect cause of sties.

When people with eyestrain rub their eyes too much, germs from their hands may cause infection. White blood cells in the body usually kill the germs that cause a sty. Then the sty softens, breaks, lets out the pus and heals.

Hot moist applications can make it break more quickly.

Sties often come one after another. Doctors can inoculate the patient with a vaccine made from the staphylococcus germs.

When sties continue for a long time, doctors may treat them with germ killing drugs.