Otitis Externa

Otitis externa is an acute, diffuse inflammation of the external auditory canal. It is often called swimmer’s ear, but swimming is only one way the canal’s protective barrier is disrupted. Moisture macerates the canal skin, while cotton-tip swabs, fingernails, hearing devices, or other instrumentation can create small abrasions. Dermatologic conditions such as eczema or psoriasis also weaken the skin barrier. Cerumen normally helps protect the canal by maintaining an acidic, water-repelling environment. When that protection is stripped away, bacteria can colonize damaged, moist tissue. *Pseudomonas aeruginosa* and *Staphylococcus aureus* are frequent causes. The usual presentation develops quickly, within 48 hours. Ear pain, itch, fullness, otorrhea, and muffled hearing may occur. Hearing is often temporarily reduced because edema and debris narrow the canal and block sound conduction; this does not necessarily mean inner-ear dysfunction. The finding that should immediately bring otitis externa to mind is pain when the tragus is pressed or the pinna is moved. Inflamed canal skin is pulled during these manoeuvres, so even gentle movement can be sharply painful.