Definition :

Swimmer's ear is inflammation, irritation, or infection of the outer ear and ear canal. The medical term for swimmer's ear is otitis externa.

This article discusses acute swimmer's ear. 

Causes, incidence, and risk factors:

Swimmer's ear is fairly common, especially among teenagers and young adults.

Causes of swimmer's ear include:

• Swimming in polluted water
• Scratching the ear or inside the ear
• Object stuck in the ear

Trying to clean wax from the ear canal, especially with cotton swabs or small objects, can irritate or damage the skin.

Swimmer's ear is occasionally associated with middle ear infection (otitis media) or upper respiratory infections such as colds. Moisture in the ear makes the ear more prone to infection from water-loving bacteria such as pseudomonas. Other bacteria, and rarely, fungi, can also cause infection.