Conjunctivitis (or pinkeye) is an inflammation of the conjunctiva (membranes that cover the eye and inner surfaces of the eyelids). Symptoms include red eyes, a discharge, tearing, and the feeling that there is something in the eye. Conjunctivitis is the most common eye disease. It may be either exogenous (resulting from various microbes or from mechanical irritation) or endogenous (arising in the presence of systemic infections, inflammations of the nasopharynx or teeth, or diseases of the gastrointestinal tract or liver). Simple acute conjunctivitis is not a serious condition, but it may give rise to grave complications. There are various severe forms, for example Egyptian ophthalmia, that causes progressive loss of sight.