Conjunctivitis is an infection of your conjunctiva, the thin lining that covers the inside of your eyelids and the whites of your eyes. Conjunctivitis can be caused by bacteria, viruses and many agents (such as dust, sand, and pollen) can also irritate your eyes. Conjunctivitis caused by viruses or bacteria spreads easily from person to person. It’s common among school children. Adults are more likely to get it if they have very dry eyes.