What causes pink eye to happen?

Contagious Viruses: Pink eye is a layperson term for viral conjunctivitis. Different types of "adenoviruses" cause infection usually in one eye. However, these viruses are highly contagious and can be spread from one eye to the other very easily. Spread from person to person occurs just as easy. "don't tell me no lies and keep your hands to yourself..." seriously, don't touch me.

Agree w/ Dr. Edwards: Virus is probably the most common cause of pink eye, but there are also other causes. See one's doc if there is cloudy thick goopy discharge as one may have a bacterial pink eye. A painful pink eye could be a sign of glaucoma. Pink eye may also be seen with auto immune disorders in which case there may be inflammation in the iris. See doc for persistent unusual uncomfortable pink eye.