By Mara Ratnofsky, DVM
Otitis externa, otherwise known as inflammation of the ear canal, affects roughly 20% of dogs. A dog with otitis may scratch his ears, shake his head vigorously and frequently, hold his ears in an abnormal position, and/or have malodorous ear discharge. The ears are also usually painful when touched.
Dogs are more prone to ear infections than members of many other species, partially as a result of their conformation. The ear canal of a dog has a steep vertical portion and then a horizontal portion, almost creating the shape of the letter “L”. This shape makes it harder for wax, oil, and other debris to make their way out of the canal, and their presence creates an environment that promotes the growth of the small amount of yeast and bacteria that normally reside in the ear canal. An overgrowth of these yeast and bacteria create the ear infection. In addition to conformation, there are other factors that can cause a dog to have excess ear wax. Ear mites, allergies (to food, fleas, pollen, etc.), tumors of the ear canal, endocrine disorders (such as hypothyroidism), and foreign material in the canals can all cause ear canal swelling and increased waxy discharge, setting the stage for infection.
A simple external ear infection can often be treated with ear cleaner and an appropriate topical medication (ear drops). The medication is usually chosen by the veterinarian after he or she looks at a sample of the ear discharge under a microscope. The microscopic evaluation will allow the veterinarian to determine if the infection is caused by yeast or bacteria, and may give some clues as to the type of bacteria present, the severity of the condition, and the chronicity of the condition. If the ear infection doesn’t respond to treatment, or if the infection returns shortly after completion of the course of medication, the dog likely has chronic otitis. With a chronic infection, the veterinarian may culture the ear debris to determine which type of bacteria is growing. This information helps the vet choose an appropriate antibiotic with which to treat. The veterinarian may also recommend flushing the ear canal to rid it of debris and to allow visualization of the ear drum which may rupture as a result of infection. In addition to treating the current infection, it is important to try to identify the underlying cause of recurrent otitis. The veterinarian may run blood tests to check for endocrine diseases, prescribe a special prescription diet to rule out food allergy, or recommend skin testing to find out if the dog is allergic to something in the environment.
If untreated, chronic inflammation will lead to an overgrowth of the tissue in the ear canal. Protrusions of excess tissue allow more places for yeast and bacteria to grow and can make the infection extremely difficult to treat. The deeper structures in the ear, including the nerves, can become affected and result in a head tilt, facial paralysis, and severe dizziness. The ear canal can become mineralized and stiff, and sometimes surgery to remove the ear canal becomes the only viable treatment option.
Ear infections are common and, if chronic, can be difficult to treat. Make sure to have your dog evaluated if he or she is showing signs of an ear infection, and follow your vet’s treatment recommendations regarding length of treatment and recheck appointments. Effective treatment early in the disease process and identification of the underlying cause will provide the best outcome for your dog.
To view a how-to video on cleaning your dog’s ears, visit: angell.org/video