Otitis externa, an inflammation or infection of the outer ear canal, is one of the more common diseases seen in the dog and cat. Animals with otitis externa often scratch at the ears and may shake their heads or rub their ears on the floor. The inside skin of the ears is usually reddened and often there is brown waxy or yellow creamy discharge in the canal signifying a yeast or bacterial infection. Excessive shaking can lead to a dilation of the ear drum or a rupture of blood vessels in the ear flap causing a hematoma. Long standing cases of otitis externa may lead to middle ear infections causing a head tilt and poor balance.
Many factors come together in the development of an ear infection. Common causes that initiate inflammation within the ear include allergies (environmental allergies, food allergy), parasites (ear mites, demodex mite, ticks), and foreign bodies (grass seeds, dried wax, hair). Factors that predispose an animal to developing otitis externa include floppy ears, excessive hair or wax in the ear canal, increased moisture by a humid environment or swimming, and obstructions of the ear canal by a growth or swelling of the ear canal tissue. Factors that perpetuate an infection are yeast and bacterial infections, proliferation of the ear canal, or treatment errors - over treatment, under treatment, inappropriate treatment or treatment reactions. Recognition and treatment of all contributing factors are the keys to successful management of ear disease.
A variety of tests may need to be performed to diagnose the cause of the otitis. Examination of the ears with an otoscope checks for the presence of discharge, inflammation, foreign objects, mites and growths. A sample of discharge is examined under the microscope to identify bacteria, yeast and/or mites. A culture may be performed on bacterial infections. Because allergies are frequently a cause of otitis, a restrictive hypoallergenic diet trial for 3-4 months and skin or blood testing for allergies along with treatment for allergies may be performed. Skull x-rays identify middle ear infections or the presence of a polyp.
Treatment begins with a thorough ear cleaning to flush out all the debris. Severe or chronic cases may require sedation or general anesthesia. Ear cleaning is then continued at home every 2-3 days. To clean the ear, fill the ear canal with cleanser until the liquid starts to spill out of the canal. Place a cotton ball in the ear so the pet will not shake out the solution. Grasp the cartilage at the base of the ear and gently massage for 3 minutes. Then remove the cotton ball and let the pet shake the cleanser from the ear. Remove loose debris from the ear flap and the entrance of the canal with a dry cotton ball or swab. Never push the cotton down in the canal as this will force debris further down into the canal.
Topical medication is applied by placing the prescribed number of drops in the affected ears. If inflammation is present on the ear flap, apply half the amount on the involved area of the flap. Massage the ear canal gently to work the medication down to the base of the ear. Oral medication may be prescribed to treat yeast or bacterial infections, inflammation or allergies. A hypoallergenic diet trial may be instituted to rule out a food allergy. Proliferative changes in the ear canal may require an intralesional steroid injection.
**If inflammation worsens or ulcerative lesions develop after starting treatment, a reaction to the cleanser or medication may be occurring. Stop the treatment and return for a recheck as soon as possible.**
Reevaluation at the hospital every 2 weeks until the ear infection resolves is vital for successful management. Your pet's ears may appear normal to you but may need continued medication and cleaning for complete resolution of the inflammation or infection. Recurrent otitis externa that is not managed properly can cause chronic irreversible changes in the ear canal, most notably a narrowing of the ear canal diameter. This narrowing does not allow medication or ear cleansers into the affected area and also does not allow the normal ear wax secretions to exit from the ear canal. Surgery to remove the abnormal canal may then be the only way to definitively resolve the problem.
Long term management may be required if the underlying problem cannot be found or corrected. In these cases a maintenance cleaning and medicating protocol is performed 1-2 times weekly. Overall control of otitis in patients with underlying allergic problems will be much easier if the allergies are well controlled with a hypoallergenic diet, antihistamines, fatty acids, hyposensitization, steroids or cyclosporine (Atopica).