Can allergies cause my dog's ear infection

Q: Why does my dog get ear infections every spring?

A: For the past month, the most common diagnosis in my practice has been allergic otitis externa, inflammation of the ear canal caused by an underlying allergy. If not caught and controlled early, allergic otitis may allow bacteria or yeast to overgrow in the ear canal. At that point the condition becomes truly an infection.

Allergic symptoms are caused by specialized cells with receptors that react to Ig-E, an antibody made in response to foreign substances. In the spring, trees, flowers, and grasses can all produce allergens that stimulate Ig-E production. Allergic patients either produce too much Ig-E or are more sensitive to it. In people, the highest concentration of Ig-E receptors is in the upper respiratory passages. That’s why we react with sneezing and sinus congestion. In dogs, the highest concentration is found in the ear canals and skin. As a result, allergies most frequently present as inflammation in the ears or itching skin.

In dogs with predicable seasonal allergic otitis, I prefer taking a preventive approach rather than waiting until symptoms develop. I typically start affected pets on an oral antihistamine during the month prior to their allergy season. During this time, I also recommend an increase in the frequency of ear cleaning to once a week. I have a strong preference for an ear cleanser with extended-release acidifiers and anti-adhesive compounds. The acidifiers make the ear canals inhospitable to yeast and the anti-adhesives inhibit bacteria.

The weekly ear-cleaning regimen can also alert pet owners to changes in wax production or irritation in the ear canal. When either is noticed, I advocate increasing the frequency of cleaning to every other day and beginning the use of a topical corticosteroid solution. The drops give the pet relief from itching and significantly reduce the irritation. It is similar to a person applying hydrocortisone ointment to a rash. 

So far, the approach I have described has not used any antibiotics or required a trip to the veterinarian (assuming prescriptions for the antihistamines and steroid drops were obtained in advance of allergy season). Many modern canine ear infections have become resistant to ordinary antibiotics. This is partially due to excessive and inappropriate use by both pet owners and veterinarians. Using topical antibiotics sporadically or for short periods of time drastically increases the risk your dog may develop an antibiotic-resistant infection. The resulting “super-bugs” could be a serious health risk to two-legged members of your family.

Antibiotic-resistant strains of bacteria that are known causes of dangerous infections in people (including Staph, E.coli, and Pseudomonas) are now routinely cultured from the ear canals of dogs. The danger is even greater when these germs develop resistance to second tier drugs, a more and more common occurrence since the introduction of topical Baytril. (I personally believe these drugs should be reserved only for aggressive infections that absolutely cannot be treated with other medications. A culture is a mandatory prerequisite for Baytril use in my practice… and the culture usually documents an acceptable alternative.)   

If the allergic otitis does progress to a true ear infection, the frequent cleaning and topical steroids will not lead to complete control of the symptoms. If that is the case, it is time for a visit to the veterinarian. Just because last year your dog developed a certain type of infection doesn’t mean the same thing is going on this year. Please do not ask your veterinarian to prescribe antibiotics without evaluating your pet. Most ear infections in dogs involve the external ear canal, however some also involve the middle or inner compartments of the ear. Mites, yeast, and several types of bacteria can are each treated with different medications. Proper treatment depends upon accurate diagnosis.

When a treatment involves antibiotics, the therapy should continue for a period of two to six weeks depending upon the species of yeast or bacteria that is being treated. Your veterinarian should recheck the deep portion of the ear canal before treatment is discontinued to ensure complete eradication of the infection.

Dr. Watts is a companion animal general practitioner and owner of Clevengers Corner Veterinary Care. He can be reached through ClevengersCorner.com or by calling 428-1000.