When a dog's ears smell, it is usually a sign that an infection is present, according to Jon Geller, D.V.M. Bacteria and yeast are the most common causes of ear infections in dogs, notes WebMD. Ear mites, allergies, excessive hair, foreign objects, moisture, wax accumulation and hypothyroidism are possible contributing factors. Dogs have vertical ear canals that make it easy for moisture and debris to accumulate.
WebMD lists other signs of ear infection as redness or swelling of the ear, shaking or tilting the head, rubbing or scratching of the ear, discharge from the ear, and crusts or scabs on the ears. Dogs with ear infections may also experience hair loss around the ear, walk in circles and exhibit problems with balance. Their hearing acuity may suffer as well.
Canine ear infections require veterinary treatment, states Dr. Geller. The vet swabs the ear and analyzes the sample to determine the cause of the infection. He then flushes the dog's ears, dries them and prescribes medication.
WebMD explains that dogs with ears that are not erect are prone to developing ear infections, especially if they have allergies or excessive amounts of hair growing in the ear canal. To prevent ear infections, a veterinarian can show the dog owner how to clean the dog's ears and clip away any excess hair. Additionally, a dog's ears should be thoroughly dried whenever they get wet.