How Does a Sty Develop?

What is a Sty?

A sty is a small, pus-filled bump that forms on your eyelid, either on the inner lining or along the lash edge. They are usually very small, only about the size of a pimple, and often have the appearance of a whitehead. However, if they become infected they can grow much larger. If a sty is big enough, it may even be difficult to open or close your eye. Because they constantly rub along the inside of your eye, sties can be very uncomfortable and irritating.

Most sties are caused by a bacterial infection in the eye, which can be contracted in a number of ways. Touching your eyes with unwashed hands, using contaminated eye makeup or not thoroughly cleaning your contact lenses can all cause bacteria to build up in the eye. However, don't be fooled into thinking good hygiene will prevent all sties: they can also be caused by chronic infections, or even stress.

When bacteria is present in the eye in higher quantities than normal, it can lead to infection. Your eyes contain glands that secrete fluids, and these are especially prone to bacteria. Buildup can cause them to become blocked or inflamed. When this happens, fluid backs up in the gland or duct. The result of gland blockage is redness, swelling in the eyelid and the formation of a pus-filled bump. Typically, sties only occur in one eye, unless the infection is spread to the other by your hands or makeup brushes. For some unfortunate people with chronic blepharitis, sties are a regularly recurring nuisance. Blepharitis is the medical term for recurrent swelling of the eyelids. Its cause is not fully understood.

The bacteria responsible for causing most sties is called staphylococcus, also referred to as staph. Staph can be found almost anywhere, including common surfaces such as telephones and water fountains. Because you come into contact with bacteria every day, it is important to always wash your hands carefully before touching your eyes or putting in your contacts. Also, periodically check the expiration dates on your makeup, and don't share eye makeup or applicator brushes with your friends. Finally, always follow the hygiene protocol suggested by your contact lens manufacturer or optometrist. With a few simple precautions, you can decrease your risk of developing the kind of bacterial infection that leads to a sty.