}}</ref>) is an inflammation of the [[conjunctiva]] (the outermost layer of the [[eye]] and the inner surface of the [[eyelid]]s), most commonly due to an [[allergic reaction]] or an [[infection]] (usually [[viral]], but sometimes [[bacterial]]<ref>Langley JM. Adenoviruses. Pediatr Rev. 2005;26:238-242.</ref>). While this article relates generally to humans, animals such as canines ([[dogs]]) and cattle can experience this condition.