Swimmer’s ear is an infection of the outer ear (the visible part of the ear, including the earlobe), ear canal or both. Also known as otitis externa, it is usually the result of excessive moisture in the ear canal, although objects placed in the ear (including cotton-tipped swabs) can also trigger the infection. Anybody can be infected with swimmer’s ear. However, it most often affects children and young adults.

Normally, water that gets into a person’s ear does not pose a health risk. The inside of the ear canal is made up of delicate skin protected by a thin layer of earwax. The ear canal lining has acidic properties that protect against infection by bacteria and fungi, which are more likely to grow in dark, warm and moist environments (such as the ear canal).  

Excess moisture can alter the balance of acid in the ear canal, allowing bacteria or fungi to multiply, leading to infection. In addition, the ear canal is easily traumatized. An injury to the lining of the canal may allow bacteria or fungi to penetrate the skin and create an infection. The canal is most often injured due to forceful cleaning using cotton-tipped swabs. The presence of foreign objects in the ear canal or physical trauma to the ear can also cause injury that can lead to swimmer’s ear.   

Bacteria called Pseudomonas aeruginosa are the most common cause of swimmer’s ear. These germs are found in soil and water. Other types of bacteria can also cause swimmer’s ear. In rare cases, a fungal infection may be responsible for the condition.

In some cases, complications associated with swimmer’s ear may arise. Some people may experience reduced hearing that lasts until the infection clears. Others may be prone to recurrent episodes of swimmer’s ear (chronic otitis externa). This can lead to infection of the surrounding skin (cellulitis).

People with certain underlying illnesses (e.g., diabetes, weakened immune system) may be more susceptible to serious complications as a result of ear infections. Bone and cartilage damage, known as malignant otitis externa, occurs when infection spreads to the bone and cartilage at the base of the skull. This is an extremely painful condition that is most likely to affect older adults and people with diabetes. It may require that a patient be hospitalized in order to be properly treated. Despite its name, cancer is not a feature of malignant otitis externa. In some cases, malignant otitis externa may spread to other parts of the body, including the brain and cranial nerves.