Foul odour coming from a dog's ears usually means the dog has an ear infection, and probably has had the infection for awhile. The smell in the ears may be accompanied by reddened ear flaps or a discharge from the ears.
Ear infections occur when the bacteria and yeast are too numerous within the ear and moisture builds up. Other causes are heredity, allergies and skin diseases.
Dogs with long ears are more likely to develop chronic ear infections because of the moisture held in by long ear flaps. Dogs with skin allergies or those with a lot of hair in the ears may also develop chronic ear infections.
Using cleaning solutions specifically for dogs' ears helps to prevent ear infections. Groomers can also help by plucking an overabundance of hair in the dog's ears.
Depending on the cause of the ear infection, a veterinarian will prescribe an antibacterial or antifungal to be applied directly into the ear. Be sure to give all of the medication, or the ear infection may flare up again.
If chronic ear infections result in thickened ear canals, surgery may be necessary to remove part of the outer ear canal. This surgery improves air circulation in the dog's ears.