Conjunctivitis (con·junc·ti·vi·tis) is an inflammation of the conjunctiva (the outermost layer of the eye and the inner surface of the eyelids), most commonly due to an allergic reaction or an infection (usually bacterial or viral)
Common causes of conjunctivitis include bacteria, viruses, and environmental factors. Viral conjunctivitis is the most common cause of infectious conjunctivitis both overall and in the adult population. Between 65% and 90% of cases of viral conjunctivitis are caused by adenoviruses