A dog ear infection — otitis externa, in the notes — is inflammation of the ear canal, usually with bacteria or yeast multiplying inside it. You normally see it before you smell it: head shaking, a paw going up to the side of the head, a dog who pulls away when you touch that ear, and a brown or waxy discharge on the inside of the flap.
The appointment itself is straightforward: our dog vet looks down both canals with an otoscope, checks whether the eardrum is intact, then reads a swab under the microscope in our in-house lab. Bacteria, yeast and ear mites look alike from the outside and are not managed the same way. Ear medication is dispensed from our pharmacy during the same visit where we have it in stock.
The harder question is why it came back. One infection is an event; a third in a year is a pattern, and the cause of that pattern can sit outside the ear: humidity, water left in the canal after a swim, thick hair at the opening, or an allergy that shows in the ears first. That is why the moisture and the hair are looked at in the same appointment, and why grooming and ear care is part of the plan for a repeat case.