Styes are caused by bacteria from your skin (usually staphylococci bacteria) that gets into and irritates the oil glands in the eyelids. These bacteria, which normally exist harmlessly on the skin of the eye, can sometimes get trapped along with dead skin cells on the edge of the eyelid. The result is a swollen, red, and painful bump that can develop over the course of a few days.

Touching mucus from the nose and then touching the eye can cause the spread of staphylococcal to the eyelid. Be sure to clean any discharge from your stye so that the infection is less likely to spread to other areas.

Reoccuring styes may indicate that eyelids need to be cleaned more often. You can do this by using a small amount of baby shampoo on a cotton swab or washcloth. Regularly washing away skin dwelling bacteria from the eyelid will decrease the risk of eyelash follicles becoming infected.

Certain things can increase your risk of developing styes. Touching your eyes without washing your hands, not disinfecting your contact lenses, and using old cosmetics can transfer bacteria to your eye. In addition, individuals with blepharitis, which is chronic redness on the edge of the eyelid, are more likely to get styes.

References

• http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002004/
• http://www.webmd.com/eye-health/understanding-sty-symptoms
• https://www.healthdirect.gov.au/stye