What causes swimmer’s ear?

Swimmer’s ear (otitis externa) is typically a bacterial infection of the ear canal; this differs from otitis media which involves fluid behind the eardrum. Otitis externa is most commonly caused by water getting trapped in the ear canal. It also follows injury to the skin of the ear canal caused by aggressive “cleaning” with Q-tips, bobby pins, match sticks and similar devices.  Use of alcohol based over-the-counter ear drops also contributes to outer ear infections.