Otitis externa is an infection of the ear canal. The organism responsible is usually pseudomonas aeruginosa. The skin of the canal may have a very varied appearance depending on the stage of the disease. It most commonly begins as an oedematous canal which becomes narrow. Debris produced by the infected skin becomes trapped in the canal. This needs to be cleaned by microsuction. After treatment, the swelling subsides to leave a more erythematous canal.