“Oto-” means ear, so “otitis” = infection, and “externa” means “external” – Otitis Externa (OE) is an infection of the Ear Canal ((see Diagrams — Upper Respiratory Tract and Anatomy of the Ear). Infection of the canal is more common in children than adults. It’s caused by bacteria that normally live there, but happen to multiply (see Differences Among Germs). High humidity can cause this, as can swimming (Otitis Externa is often called “swimmer’s ear,” but you can get it even if you don’t swim).
Diagnosis is easy — a patient has new ear pain. We pull on the pinna or push on the tragus (see diagram), which serves to wiggle the canal. If that really hurts, then the canal is infected. Doing this doesn’t hurt a bit with middle ear infection (Otitis Media). We also examine the ear canal with an otoscope (the instrument hanging on exam room walls), to look for exudate (whitish gunk consisting of pus mixed with ear wax).
Treatment is easy — antibiotic ear drops almost always work. It’s best to use a kind without the medication neomycin, which causes lots of skin allergies. The problem with ear drops is that if the ear canal is swollen & full of exudate, the drops can’t get in. So the patient needs to lie on their side with the ear up, for about 5 minutes. Rarely, oral antibiotics which treat Staph may be necessary.
A rare complication is called “Malignant Otitis Externa” (nothing to do with cancer). Bacteria spread from the ear canal into nearby skin & even bone. The area around the ear is red and warm, and tender to touch. These patients need oral or even IV antibiotics (especially if there’s a fever). This complication usually only happens to people with severe diabetes or other diseases that interfere with our immune system.