Pink eye is an inflammation or infection of the conjunctiva, the transparent membrane lining the eyelid and part of the eyeball. It is the most common type of eye infection and is most likely to affect preschool-age children. Pink eye is also known as conjunctivitis.

Bacterial and viral infections are often the cause of pink eye. People may become infected after coming into contact with the tears or discharges from the eyes of an infected person. People with pink eye who also have an upper respiratory infection can spread the illness through droplets that are disseminated when coughing or sneezing.

Pink eye also can develop from noninfectious sources, such as allergies, foreign objects that become lodged in the eyes, and exposure of the eye to a chemical or other irritant (e.g., shampoos, dirt, smoke, pool chlorine).

Symptoms of pink eye usually appear anywhere from a couple of days to a couple of weeks after the person has been exposed to the source of the illness. People with pink eye may feel like they have something stuck in one or both eyes. As blood vessels in the conjunctiva swell, a pinkish tinge may develop in the whites of their eyes, which gives the condition its common name. Discharge from the eyes also is common.

Because infectious pink eye is highly contagious, people who have symptoms of this illness are urged to seek prompt medical attention. There is no treatment available for viral pink eye other than to let the virus run its course. Antibiotics may be prescribed to treat bacterial pink eye and can clear the infection in just a few days.

The best way to avoid pink eye is to take precautions against factors known to cause conjunctivitis. This means avoiding close contact with people who have viral or bacterial pink eye. People who are diagnosed with infectious pink eye are urged to remain home from school or work until at least 24 hours after treatments have begun or drainage from the eye has stopped.