Conjunctivitis, more commonly known as pink eye, is an infection and inflammation of the conjunctiva, the membrane that lines the eyelid and eyeball. The inflammation affects the blood vessels and gives the eye a pink or red appearance. Conjunctivitis (pink eye) is caused by a bacterial or viral infection and can be contagious, so diagnosis and proper treatment are important. It can also be caused by an allergic reaction or a foreign object in the eye. Symptoms of conjunctivitis (pink eye) include redness and itchiness in one or both eyes, along with a discharge that may turn into a crust overnight. Excess tearing can also occur. Treatment for pink eye depends on the cause. Your doctor may prescribe antibiotic eye drops or recommend over-the-counter drugs.