Ear Infections in Cats and Dogs

     Ear disease is one of the more common diseases in dogs. Infection of the ear or otitis can occur in the external or middle ear. Clinical signs of ear infections include – head shaking, scratching at the ears, a stinky ear, discharge, swelling or redness of the skin inside the ear. Not all red ears are infected ears, however, if they are left untreated it can become infected.

     The normal ear is a structure made up of cartilage that is lined with skin, hair follicles, sebaceous (sweat glands) and modified ceruminous (wax forming) glands. Normally the skin cells and glandular cells produce wax to trap dirt and debris in the ear canal. The normal ear canal is smooth, light pink, with a pearly appearing tympanic membrane.

     The development of ear infections can be divided into predisposing, primary and perpetuating factors. Predisposing factors include the environment such as moisture and or heat, hair plucking, grooming powders and/or anatomic variation; floppy ears (like cocker spaniels), stenotic or narrow ear canals (like the sharpei), and the number of wax/ glandular cells, and number of hair follicles lining the ear canal. Other predisposing causes include hormonal or autoimmune diseases.

     Primary causes include foreign bodies (foxtails), cancer, ear mites, food/inhaled allergies, endocrine or autoimmune diseases.

     Perpetuating factors – these are causes that make treatment challenging and prone to failure –include bacterial or yeast infections, chronic changes to the structure of the ear from inflammation or deep infection, or inappropriate treatment.

     Determining ear infections begins with an otoscopic examination – to assess the surface of the ear canal and to determine if the ear drum is intact. Next is obtaining a sample of the material in the ear by rolling the exudates (wax) onto a slide. There we look for yeast and/or bacteria or even parasites!

     If bacteria or yeast are seen, we need to clean out the ear wax and debris using a special ear cleaner. In order for a medication to work and adhere to the skin in the ear, we need to start with a clean dry ear. If some infections are very deep we may need to add oral antibiotics and steroids to decrease inflammation.

     Maintenance ear care prevents ear infections from occurring again. Depending on your veterinarian they may recommend routine ear cleanings with an appropriate cleaner and medication. Over cleaning can also predispose our pets to developing ear infections by disrupting the normal microenvironment in the ear. Successful treatment of ear infections require identification of the primary cause (allergies, foreign body, autoimmune, endocrine diseases etc), and choosing the appropriate antibiotic along with regular visual assessment of the ear canal and tympanic membrane by your veterinarian.

Caroline Li, DVM