A stye is a small bump that can appear on the outside or inside of the eyelid.
Styes are caused by a bacterial infection. Usually the bacteria grow in the root (follicle) of an eyelash. An internal hordeolum is caused by infection in one of the tiny oil glands inside the eyelid.
A stye usually starts as a red bump that looks like a pimple along the edge of the eyelid.
As the stye grows, the eyelid becomes swollen and painful, and the eye may water.
Most styes swell for about 3 days before they break open and drain.
Styes usually heal in about a week.