A sty (stye) is an inflammed oil gland of the eyelid that appears as a red, tender pimple.
It is caused by a bacterial infection of the gland. Usually, the sty drains & heals on its own. If the gland becomes blocked, it is called a chalazion
and may need to be lanced by a doctor. You can treat a sty by applying a warm compress for 10 min 4x/day. Do not squeeze it!