Acute cases are typically due to bacterial infection, and chronic cases are often due to allergies and autoimmune disorders.The most common cause of Otitis externa is bacterial. Risk factors for acute cases include swimming, minor trauma from cleaning, using hearing aids and ear plugs, and other skin problems, such as seborrhoea (dandruff), psoriasis and dermatitis.

People with diabetes are at risk of a severe form of disease called malignant otitis externa. This disease causes progressive destruction of external ear tissues and can spread deep inside the ear. Diagnosis is based on the signs and symptoms.Culturing the ear canal may be useful in chronic or severe cases. Pain is severe and is usually indicative of an active disease. Controlling the blood sugar and giving prolonged appropriate antibiotics is the treatment of choice.