Otitis externa (external ear inflammation)
Otitis externa is inflammation of the external ear canal (from the eardrum to the tip of the ear). It is common in dogs, and is a particular problem in breeds like Cocker Spaniels, Labrador Retrievers, Golden Retrievers, Springer Spaniels, and others.
We are in the habit of talking about ear "infections". Most dogs have inflammation (redness, swelling, pain, and heat) of the ear canals long before infections develop. When skin becomes inflamed its ordinary defenses are weakened. The skin is moist and warm, making a nice breeding ground for organisms. The waxy protective coating is often lost, allowing organisms in. Thus all ear "infections" are actually secondary infections resulting from an established inflammation.
There are often other factors that make a simple ear inflammation more complicated
- secondary infections with Malassezia (a type of yeast)
- secondary infection with bacteria
- swollen, thickened ear canals (difficult to medicate)
- middle ear infection
So what makes some dogs get otitis but not others? The primary factors associated with external ear disease are:
- *allergies (atopy or food sensitivity)
- parasites (ear mites, skin mites)
- foreign bodies like grass seeds
- hormonal problems
- zinc responsive dermatosis
- immune-mediated disease
Unless the cause of the otitis is addressed, the problem is unlikely to resolve satisfactorily.
Identification of underlying problems
We may need to perform one or many of the following procedures in order to determine what has caused the ear to become inflamed. We will perform the tests in a logical order designed to minimize costs and maximize our chances of obtaining a correct diagnosis.
- Ear cytology (examination of swab material under the microscope, identifies cells and organisms)
- Ear flush and examination under sedation
- Culture for bacteria, with antibiotic sensitivities
- Skin biopsy
- Treatment for scabies mites
- Hypoallergenic food trial
- Allergy testing
Middle ear infections
Secondary infections of the external ear canal with either yeast or bacteria can lead to middle ear infections. In some cases the inflammation and infection in the external canal is severe enough to rupture the eardrum that separates the middle and external ear canals. When the eardrum ruptures the infection spreads to the middle ear. This is especially true of yeast infections.
If the eardrum cannot be seen with the ear scope with the dog awake, we will need to sedate or anesthetize him, flush the debris from the canals, and evaluate the eardrum. We will need to give systemic (oral) antifungal or antibiotic medications if the eardrum is missing; topical medications simply cannot get into the middle ear. If the eardrum is intact, topical antibiotic or antifungal medications may be all that are necessary. In all but a very small number of cases the ruptured eardrum repairs itself once the inflammation and infection are cleared up.