A stye is basically a staph infection that attacks the sebaceous gland at the base of an eyelash. As you probably know, these glands, which secrete the protective oily substance known as sebum, are attached to most hair follicles, and the eyelashes are no exception. Styes can be extremely painful considering how small they are, although sometimes they grow quite large - the inflammation can sometimes be enough to cause the entire eyelid to swell.
Usually, a stye takes a natural course of three or four days, or sometimes up to a week, during which time it will continue to swell and finally burst and drain on its own. In spite of the pain, styes are quite harmless; the only other symptoms apart from the inflammation and pain are a little itching and watering of the eye. Treatment is usually not required, but if you want, you can apply a warm compress to the eye several times through the day. This is mainly to ease the pain, but it also seems to make the stye drain faster. If you do this, you should make sure that the cloth you use is clean and soft. When the stye does burst on its own, you should clean the area carefully with plain water. Avoid touching it too much, else you will end up with a secondary infection. While the stye is present and for a few days after it bursts, you should also avoid using any make up or wearing contact lenses.
If a stye is particularly painful or does not drain within a week, it may need to be lanced - this should ALWAYS be done by a doctor. Bursting pimples is bad enough, but bursting a stye on your own is even more dangerous. Your doctor will lance the stye carefully, or may even prescribe an ointment for a few days.
answered by G M