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Ear Infections in Dogs and Cats

Written by Heather Norton-Bower, DVM.



As many owners know far too well, ear problems in dogs and cats can be incredibly uncomfortable. The scratching, head shaking, and self-trauma that is associated with ear infections or ear inflammation can be incessant and may even keep pets and owners up in the middle of the night.

Besides the relief that owners seek for their itchy or painful feline and canine companions, owners want to know what causes ear problems. Especially when the ear problems are recurrent or chronic, it is helpful to understand some of the potential causes.

Are canine/feline ear infections similar to ear infections in people?

Most canine and feline ear infections only involve the external ear. In humans, the disease most often involves the middle ear. Whereas a respiratory viral and/or bacterial illness is often the culprit behind ear infections in people (think the common cold), ear infections in cats and dogs are set off by inflammation from a variety of causes. Another difference is that cats and dogs usually don't "outgrow" ear infections, but in people it is usually children that are affected and with age the problem will resolve.

How does inflammation cause an ear infection?

Normally the inside of the ear flaps and the ear canals are lined by a happy, healthy outer skin layer (the epithelium). When inflammation is present, this layer becomes reddened, thickened, and sometimes very swollen. This inflammation alone can make a pet go crazy with itching. The itchiness factor rises exponentially when bacteria and yeast that are normal inhabitants of the skin and ear canals thrive on this inflamed surface and overpopulate. Ear infections involve this overgrowth of yeast and/or bacteria and the higher populations of these organisms help perpetuate the underlying ear inflammation. First comes the inflammation, and next comes the infection. However, like in most areas of medicine, we often refer to ear inflammation alone as an "ear infection".

What are some causes of inflammation in the feline and canine ear?

Ear Mites: Seen more commonly in cats, especially if the cat is an indoor-outdoor cat or previously a stray. The mites make the ears intensely itchy and owners will often find evidence of self-trauma to the ears or skin around the ears. Usually mites are easily identified under the microscope (and sometimes during the ear exam itself) and treatment can be an easy-to-use topical product. All pets in a household, even those that are without symptoms, should be treated for ear mites when we diagnose a pet with this issue. Otherwise, asymptomatic carriers may be a source of re-infection.

Food Allergy: This is a sensitivity or intolerance to an ingredient in the diet (usually the protein source). More common in dogs than cats. In dogs, it may occur at any age, but about 30% of dogs diagnosed with food allergy are less than one year of age. Ear infections are seen in up to 80% of dogs with food allergies and in 20% of these dogs, this is the only symptom. Sometimes other areas of the skin are involved, other times the ear problems are the only symptom. A special diet using a protein that is "new" to the pet or "broken" into small components that the immune system doesn't detect is usually the solution. The right diet is determined by diet trials that usually last at least 3 months.

Atopy: Involves a hypersensitivity reaction to environmental allergens, such as dust mites or pollens. In cats, this is uncommon and less common than food allergy. The problem is very common in dogs, where age of onset usually ranges from 6 months to 6 years and symptoms typically appear between 1 and 3 years of age. Ear problems are seen in 50-80% of atopic dogs and in about 5% of these dogs, this is the only symptom. Within our canine population, we see many more ear infections in the spring, summer, and fall when pollen is a factor. Atopy is a rule out diagnosis since even normal animals will have positives on the intradermal skin testing or blood tests that we use to come up with hyposensitization therapy (allergy shots). Allergy shots and drugs that keep the immune system from reacting against the allergens are the therapy of choice in the case of recurrent ear infections where therapies such as antihistamines, fatty acid supplementation, or topical therapies have failed to decrease the frequency of ear infections. Steroids can also be used for shorter term relief, especially if the allergy problem is seasonal. It is not uncommon for dogs to have both food allergies and atopy at the same time.

Hypothyroidism: Before a dog with year-round ear problems is considered to have a food allergy or atopy, hypothyroidism (low thyroid levels) should be ruled out with a blood panel test. This disease is easy to correct with a very safe and daily medication.

Defects in keratinization: This involves excessive secretion of wax in the ear. Some breeds like Cocker Spaniels have more problems with ears when both keratinization defects and otitis externa are present.

Inflammatory polyps: A disease that uncommonly affects our cat population. Polyps (a type of benign mass) originate from the lining of different parts of the feline ear or even the nasopharynx (area at the back of the mouth by the throat). Symptoms can be chronic one-sided ear infections or respiratory in nature, depending on where the polyp originates. Surgery is the way to correct polyps.

What diagnostics are necessary to diagnose ear infections?

A visual inspection of an itchy ear that is inflamed will show reddened, irritated, and often swollen ear flaps and ear canals. Along with seeing signs of inflammation, the presence of malodorous debris indicates there is a secondary infection of the ear. Microscopic examination of material collected on an ear swab is the way to definitively diagnose an ear infection and can sometimes identify the cause of the inflammation (mites). This cytology is important because it allows us to find out what organisms are involved in the problem (may be similar or very different from time to time) and it guides therapy. It also helps us determine the severity of an infection. Some ear infections caused by secondary overgrowth of the rod-shaped bacteria called Pseudomonas can be quite painful and difficult to treat, often requiring non-routine medication for resistant bacteria. When we see rod-shaped bacteria under the microscope, the ideal is to run a culture and sensitivity on a sample of the ear material.

How are ear infections treated?

Part 1: One aspect of treating ear infections is addressing the potential overgrowth of yeast and/or bacteria in the ear. Unless we are dealing with the rare case of an inner ear infection (otitis media), topical medications are used to bring yeast and bacteria back into equilibrium. Depending on the presentation, topical meds will normally be used for 1-2 weeks and most are administered twice daily. If a culture and sensitivity was performed on the ear, then specific medication directed towards a given bacteria will be chosen. In some cases (such as treatment for some cases of Pseudomonas bacterial overgrowth), the medication is placed in an ear cleaning solution and this solution is used to fill up the external ear canal once to twice daily.

Part 2: Treatment is also directed at the inflammation that prompted the "ear infection" in the first place. Many of our topical medications directed against yeast/bacteria will also contain an anti-inflammatory. If the degree of inflammation is very severe, however, your veterinarian may prescribe a short course of an oral steroid medication. If ear infections are chronic and reoccur over and over, then we work to find a plan that helps "control" the ear infections. This may be treatment for hypothyroidism if the pet is found to be hypothyroid. Or it could be a new diet in the case of food allergies. In the case of atopy, it might mean something as easy as anti-inflammatory drops used every other day to once weekly in the ears, taking daily antihistamines and fish oil supplements, or switching to a diet that is high in omega fatty acids that promote healthy skin. When these fail to help our itchy pets, allergy shots or medications to "fool" the immune system can make all the difference.

Part 3: Besides antibacterial, antifungal, and anti-inflammatory treatment, ear cleaning is an important aspect of treating and preventing ear infections in dogs. The frequency depends on the severity of the infection. It may be recommended once weekly to every few days during the treatment of the ear infection. Ear cleaning solution is pH balanced to be less irritating to ears and it will make the ear less inviting for yeast and bacterial growth. It also helps remove accumulating debris related to inflammation and yeast/bacteria. Ear cleaning steps: 1) Fill the entire external ear canal with solution. There is no such thing as too much, but too little results in no help at all. 2) Massage the base of the ear (where ear attaches to head) for about 30 seconds. 3) Gently remove debris from canal with gauze squares or cotton balls. Resist the temptation to use cotton swabs as these tend to pack material further down into the canals and may also increase risk of ear drum rupture if your pet is squirmy. Cleaning out the ears regularly (even sometimes once weekly) is often advised for dogs with frequently reoccurring ear infections. In those pets, it is also very important to clean their ears after swimming or taking a bath as these activities predispose pets to ear inflammation/infections.

Part 4: The ears should be rechecked when therapy is done, or earlier if the ears fail to show improvement at home. A visual inspection of the ear canal with a special tool called an otoscope allows us to determine if an infection has resolved. The recheck visit is also a great time to talk about long-term therapy if the problem has been recurrent.

Why is it important to treat ear infections in cats and dogs?

Treating ear infections as they arise helps pets avoid pain and discomfort. It also decreases the risk of serious long-term problems. From chronic inflammation, the ear canal "remodels" and this particular remodeling project further predisposes the ear to more inflammation and secondary infections. At the same time, it becomes harder and harder to clean the ears and apply medication. After years of "bad remodeling", the ear canals and the cartilage associated with the ears may actually harden to the point that all medical therapy fails to help. At that point, surgery to alter the ear canal is indicated. Hearing in chronic cases may be compromised and if surgery is indicated, permanent hearing loss is often the end result. Finding the right combination of therapy for chronic ear problems is therefore very important in providing both short-term and long-term quality of life.

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