Swimmer’s ear, also called otitis externa, is an exquisitely painful infection of the ear canal that leads to the ear drum. According to the American Academy of Otolaryngology-Head and Neck Surgery, any activity that allows water to enter your ears can cause it. This includes showering, washing your hair, even using a sauna. In fact, just being in a warm, humid climate could do it.
The skin of the ear canal is normally protected by a thick coating of earwax. When water enters the ear, it may bring bacterial or fungal particles. If the water runs back out, the ear dries out and the bacteria and fungi don't cause any problems. But sometimes water remains trapped in the ear canal, washing away the earwax and allowing the skin to get soggy. Then the bacteria and fungi flourish and can infect the outer ear. The infection can be cured with ear drops.
See a doctor if any of these symptoms occur:
Your ears feel blocked or itchy.
The ear canal becomes red or swollen, perhaps even swelling shut.
A milky fluid drains from your ear.
The ear becomes painful and tender to touch, especially the cartilage in front of the ear canal.