Otitis externa in dog and cats

Otitis externa, or inflammation of the external ear, is relatively common in dogs and cats. Causes include excess humidity/ water in the ear canal, ear mites, or it can be a manifestation of a more generalised skin problem such as allergies or atopic dermatitis. Clinical signs include redness of the skin of the ear flap or canal, itchiness, headshaking, odour, excessive ear discharge and pain when cleaning the ear.

The general anatomy of the ear canal is as follows:

A small amount of light brown ear wax is normal when cleaning the ears. However, inflammation usually results in excessive discharge in both the horizontal and vertical canals. The ear flap and skin near the ear opening may be inflamed or have injuries from self-trauma. 

To properly treat otitis externa, the vet needs to find out the underlying cause. This usually involves visualisation of the ear canal using an otoscope as well as taking a smear of the ear discharge. The smear is then examined under the microscope to determine if the discharge comprises parasites (ear mites) or microorganisms (such as bacteria or yeast).

If the inflammation is severe, your pet might require sedation for a proper ear examination to assess the ear drum. Sedation also allows for a thorough cleaning of the ear canal. In cases where the ear drum has ruptured due to severe infection, special ear cleansers and medication will be required to reduce risk of deafness.

Treatment of ear infections vary depending on the cause. An infection due to bacteria or yeast will require the appropriate antibiotic or antifungal ointment. If the ear is swollen or painful, oral anti-inflammatories may also be prescribed to increase comfort and allow ease of cleaning and application of ointment. It is important to clean off any excessive ear discharge daily before instilling topical medication, so that the medication can penetrate effectively. Ear mites are treated differently, usually with topical anti-parasitics. It is vital to treat all in-contact pets if mites have been diagnosed.

If your pet suffers from recurrent ear infections, or has a concurrent skin condition, further investigation into an underlying allergy is recommended. This may involve elimination diet trials, blood or skin testing for allergens etc.