Brown discharge from a dog’s ears may be caused by ear mites, and the dog needs to be treated promptly to prevent the ear mites from getting worse or spreading. First, drop ear cleaning liquid into the dog's ears, rub it gently for a minute, and then use a cotton swab to wipe away the brown secretions in the dog's ear canal. Do not wipe too hard to avoid damaging the dog's ears. It is best to clean your dog once a week until the ear mites are gone.