Conjunctivitis is inflammation of the delicate surface membrane that normally forms a thin, transparent covering across the eye and folds back up inside the eyelid.
Conjunctivitis causes redness of the conjunctiva (the white of the eye and inside the eyelids), usually of both eyes. The eyes may be sore, itchy, burning and sometimes extremely painful. Bright light can make the condition seem worse.
If the cause is a bacterial infection, the eye may discharge a white/yellow sticky pus. This can crust on the eyelashes and glue the eyelids together, especially after sleep.
If an allergen is causing the conjunctivitis, the eyes may be swollen, itchy and produce a thin, watery discharge. Viral conjunctivitis usually lasts a matter of days, and complications are extremely rare.
For most people, the infection clears up within a week without needing specific treatment. Antibiotics make very little difference, so nowadays they're less often recommended. However, infections that are particularly severe or last more than two weeks may be treated with a course of Antibiotics.