Conjunctivitis is inflammation or infection of the membrane lining the eyelids (conjunctiva).
The conjunctiva is exposed to bacteria and other irritants. Tears help protect the conjunctiva by diluting bacteria and washing it away. Tears also contain enzymes and antibodies which kill bacteria.
There are many causes of conjunctivitis. Viruses are the most common cause. Other causes include bacteria, chlamydia, fungus, and rarely, parasitic agents.
"Pink eye" refers to a viral infection of the conjunctiva. These infections are especially contagious among children. Handwashing is key to preventing the spread of the virus, which is similar to the type that causes the common cold.
Sources
MedlinePlus - Conjuntivitis
