“Conjunctivitis” (often called pink-eye) means inflammation of the conjunctiva (kon-junk-TI-vuh). The conjunctiva is the thin membrane that covers the white part of the eye (sclera) and the undersurface of the eyelids. “Inflammation” means that this membrane is red, irritated, or swollen.
Conjunctivitis is not a disease; it is simply a reaction to something that is irritating the eye. There are many conditions that can result in a reddened eye. Usually, it means a viral or bacterial infection, but conjunctivitis can also be caused by allergy, irritants such as air pollution, smoke or noxious fumes, or minor trauma as from contact lenses, a scratch, or even a loose eyelash. An eye can also look red as the result of something more serious, such as corneal infection or foreign body, or even be a sign of certain inner eye diseases.