What is it?
A sty (hordeolum) is a red, painful lump near the edge of your eyelid that may look like a boil or a pimple. Usually a sty is filled with pus. A sty most commonly forms on the outside of your eyelid, but sometimes a sty can form on the inner part of your eyelid.
In most cases, a sty will disappear on its own in a few days to a week. In the meantime, you may be able to relieve the pain or discomfort of a sty by applying a warm washcloth to your eyelid.
Signs and symptoms of a sty include:
- A red lump on your eyelid that is similar to a boil or a pimple
- Eyelid pain
- Eyelid swelling
A sty can be caused by:
- Poor hygiene that exposes your eyelids to bacteria. A sty is commonly caused by the bacterium staphylococcus, though other bacteria can also cause a sty. Touching your eyes with unwashed hands can transfer bacteria to your eyelids.
- Eyelid inflammation. Chronic inflammation along the edge of the eyelid caused by a condition called blepharitis can cause a sty to form. Following your doctor's instructions for treating your blepharitis can help prevent sties.
You risk exposing your eyelids to infection if you:
- Change your contact lenses without thoroughly washing your hands first
- Fail to disinfect your contact lenses before putting them in
- Leave eye makeup on overnight
- Use old or expired cosmetics
Tests and procedures used to diagnose a sty include:
- Examining your eyelid. Your doctor may determine you have a sty by looking at your eyelid. Your doctor may use a light and a magnifying device to examine your eyelid.
- Testing for bacteria. If your doctor needs to lance your sty to relieve pressure, a small sample of pus may be collected for testing. This helps determine which bacterium is causing your infection and which antibiotics are most appropriate for you.