Swimmer's ear is an infection of the ear canal.  Your ears' protective features work best when they are dry. If your ear canals are exposed to excess moisture, if you swim a lot, they're more likely to become infected. Swimmer's ear is also known as acute external otitis or otitis externa.  Swimmer's ear is usually easily treated. Prompt treatment of swimmer's ear can help prevent the development of more-serious complications and infections. Swimmer's ear happens when bacteria grow in the ear canal, which is a passageway to the eardrum. In that canal, you'll find delicate skin that's protected by a thin coating of earwax. Most of the time, water can run in and out of the ear canal without causing a problem.  Bacteria get a chance to grow when water stays in the ear canal and it washes away the protective coating of earwax. A lot of swimming can wash away that wax protection and lead to these wet conditions in the ear canal. Bacteria grow and the ear canal gets red and swollen. Sometimes kids can get an infection in the ear canal even if they haven't been swimming. A scratch or other irritation to the ear canal can also lead to swimmer's ear.