If you notice your dog scratching his ear, shaking his head, or smelly colored discharge coming from his ears, your dog may have an ear infection. Ear infections are common problems in dogs and can occur in the outer, middle or inner ear. Ear infections usually begin with inflammation of the outer ear canal, caused by bacteria or yeast. But, ear infections in dogs can be caused by food allergies, parasites, foreign bodies, trauma, excess moisture in the ear or hereditary conditions. If you think your dog has an ear infection, take him to the vet for treatment. Then learn how to prevent ear infections and properly clean your dog’s ears.