Pet Columns, Office of Public Engagement, College of Veterinary Medicine at the University of Illinois at Urbana-Champaign

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The Amazing Truth About Ears


Pet Column for the week of May 20, 2002


Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Jennifer Stone
Information Specialist

"Oh no! Rover is scratching at his ears again!"

Ears infections cause great frustration for owners and pain or discomfort for animals. They are one of the main reasons for pet owners to visit their veterinarian. Common signs of ear infection include head shaking, frequent scratching, foul odors, abnormal discharge, redness, and pain. Although the ear may seem like a very simple structure, it is actually a complex organ that can become irritated because of a whole host of primary causes and contributing factors.

In cats and dogs, the external part of the ear consists of the pinna, the ear canal, and the eardrum. The ear canal consists of a vertical part (the part you can see when you look inside the ear) and a horizontal part, which extends deeper to the eardrum.

Dr. John Angus, a resident in veterinary dermatology at the University of Illinois Veterinary Teaching Hospital in Urbana, says, "This abrupt angle in the ear canal is a normal anatomical feature that makes cleaning difficult and can help trap debris and wax inside the ear."

Many factors can make ear infection more likely. Things that increase moisture and decrease ventilation can contribute to infection. Animals that like to swim or that have a naturally narrow ear canal can be at risk. Excessive hair or floppy ears can also trap moisture inside the ear. While these factors may predispose your pet to infection or make a current infection worse, by themselves they do not cause infection.

In addition, owners sometimes make infections worse by using water or irritating substances such as straight rubbing alcohol or vinegar to clean the ear, or by causing trauma to the ear canal by over-aggressive cleaning. Water increases moisture within the ear and does not evaporate adequately deep in the canal. Irritating substances can damage the fragile lining of the ear canal, making it more susceptible to bacterial infections. Only gentle cleansers designed for use in the ear canal should be used. Prescription ear cleansers available from a veterinarian may be used to treat specific disorders or infections. Use of cotton swabs is not recommended because they tend to pack the earwax into the ear canal, making it more difficult to remove.

Surprisingly, bacteria and yeast are not considered a cause of ear disease; rather they are considered the result of inflammation of the ear canal.

"An infection of the external ear is almost always a sign of an underlying disease," says Dr. Angus. "Changes in the ear canal resulting from the underlying cause allow normal bacteria and yeast to overpopulate. Eventually the overgrowth becomes infection and results in ongoing disease even after the initial cause has resolved."
The most common underlying cause of ear problems in dogs is allergic reactions. The pollens and molds that cause hay fever symptoms in people are the principal causes of skin and ear disease in dogs. Dogs can also become allergic to an ingredient in their food, even after they have been eating that food for years. (If you suspect your dog has an allergy, contact your veterinarian for directions on managing these conditions.)

Other causes for ear infections include foreign objects that become lodged in the ear, ear mites, polyps, or tumors within the ear canal.

Successful management of ear disease requires both identification of the primary cause and management of secondary infection. Addressing just one or the other is a common reason for treatment failure. If the ear canal remains inflamed and infected for a long time, infection may move across the eardrum to the middle ear.

Over time or in certain breeds of dogs, such as cocker spaniels, the ear canal becomes thickened or even mineralized, causing it to be inflexible. Once the ear canal is mineralized, changes may be irreversible and require surgery to relieve chronic pain.

If your animal's ear problem has been treated several times with little improvement, it may be time for your veterinarian to dig a little deeper for the root of the problem. Dr. Angus says, "Unless you stop the cause of the problem, the infection may never go away."

If you suspect that your pet has an ear infection, please contact your local veterinarian.