Ear Infections in Dogs (Otitis Externa)

By Malcolm Weir, DVM, MSc, MPH; Amy Panning, DVM; Ernest Ward, DVM

Infection of the external ear canal (outer ear infection) is called otitis externa and is one of the most common types of infections seen in dogs. Some breeds, particularly those with large, floppy, or hairy ears (e.g., Cocker Spaniels, Miniature Poodles, Old English Sheepdogs, etc.), are more prone to ear infections, but they can occur in any breed.

What are the clinical signs of an ear infection?

Ear infections are painful. Many dogs will shake their head and scratch their ears to relieve the discomfort. The ears often become red and inflamed and develop an offensive odor. A black or yellowish discharge commonly occurs. In chronic cases, the ears may appear crusty or thickened, and the ear canals often become narrowed (stenotic) due to chronic inflammation.

Don't these signs usually indicate ear mites?

Ear mites can cause several signs, including a black discharge, scratching, and head shaking. However, ear mite infections are more common in puppies and kittens. Adult dogs may occasionally contract ear mites from infected puppies or cats. Ear mites create an environment within the ear canal that often leads to a secondary bacterial or fungal infection.

"Ear mites create an environment within the ear canal that often leads to a secondary bacterial or fungal infection."

Since the signs are similar and usually mean an infection, why can't I just get some ear medication?

There are several kinds of bacteria and at least one type of fungus that commonly cause ear infections. Knowing the specific kind of infection present makes it impossible to know which medication to use. Sometimes, the problem is a foreign body, a polyp, or a tumor; treatment with medication alone will not resolve these problems. Your dog must be examined to ensure the eardrum is intact. Administration of certain medications can result in hearing loss if the eardrum is ruptured. This can only be detected by a thorough ear examination by your veterinarian.

How are ear infections diagnosed?

dog-earcanal_updated2017-01-01First, the ear canal is examined with an otoscope, an instrument that provides magnification and light. This examination allows your veterinarian to determine whether the eardrum is intact and if there is any foreign material in the canal. If your dog is in extreme pain and refuses to allow the examination, it may be necessary to sedate or anesthetize him for a thorough examination.

"If your dog is in extreme pain and refuses to allow the examination, it may be necessary to sedate or anesthetize him for a thorough examination."

The next step is to examine a sample of the material from the ear canal under a microscope to determine the type of organism causing the infection. Microscopic examination is essential in helping your veterinarian choose the right medication to treat the inflamed ear canal. Culture and susceptibility tests are often used in severe or chronic ear infections to ensure your dog receives the right medication.

How are ear infections treated?

The otoscopic and microscopic examination results usually determine the diagnosis and course of treatment. If there is a foreign body, wax plug, or parasite lodged in the ear canal, it will be removed. Some dogs must be sedated for this or to allow a thorough ear flushing and cleaning. Many dogs will have more than one type of infection (e.g., bacterium and fungus or two kinds of bacteria). This situation usually requires the use of multiple medications or a broad-spectrum medication. See the handout “Applying Ear Drops to Dogs” for a step-by-step guide to administering ear medication to your dog.

An important part of the evaluation of the patient is identifying an underlying disease. Many dogs with chronic or recurrent ear infections have allergies; allergies are a component of ear infections in as many as 43% of cases. Furthermore, ear infections occur in 65-80% of dogs with underlying food allergies. If your veterinarian suspects a food allergy, an elimination diet trial may be recommended to see if it breaks the repeated infection cycle; this involves feeding your dog a diet that contains a type of protein that your dog has not been exposed to. The immune system will not recognize and react to the new protein, which may reduce your dog’s symptoms.

"...ear infections occur in 65-80% of dogs with underlying food allergies."

Other underlying diseases that can lead to repeated ear infections include hormonal issues like hypothyroidism. Regardless, if an underlying disease is suspected, it must be diagnosed and treated, or your dog will continue to experience ear problems.

Closing of the ear canal is another result of a chronic ear infection. This is known as hyperplasia or stenosis. If the ear canal is swollen, it is difficult or impossible for medications to penetrate the horizontal canal. Anti-inflammatory medications can sometimes shrink the swollen tissues and open the canal in some dogs. Most cases of hyperplasia will eventually require surgery.

What is the goal of ear canal surgery?

Several surgical procedures are used to treat this problem. The most commonly performed surgery is called a lateral ear resection. The goal of the surgery is to remove the vertical part of the ear canal and eliminate the swollen tissue from the horizontal canal. Removing the vertical canal is relatively easy but removing large amounts of tissue from the horizontal canal is more complicated. In some cases, it is necessary to remove the entire ear canal (total ear canal ablation), which may result in permanent hearing impairment. See the handout "Total Ear Canal Ablation and Bulla Osteotomy (TECA-BO)" for information on this surgery.

What is the prognosis?

Nearly all ear infections that are diagnosed and treated can be successfully managed. However, if an underlying cause remains unidentified and untreated, the outcome will be less favorable. Several recheck examinations may be needed before the outcome is successful.

How important is it to treat an ear infection?

Dogs with ear infections are uncomfortable. Their ears are a source of constant pain, and they frequently scratch them and shake their head. This can cause an aural hematoma, in which blood vessels in the ear flap break, causing a painful swelling that requires surgical treatment. Deep ear infections can damage or rupture the eardrum, causing an internal ear infection and even permanent hearing loss.

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