[From Tufts May 2012 Issue]
To many people, the smell of baking bread evokes recollections of home cooking. But if your dog’s ears emit a similar odor, it’s cause for concern: You need to put in a call to his veterinarian. It’s a sign that he may have a yeast infection — a condition that, if left untreated, can lead to significant discomfort, complications and even partial deafness on those rare occasions when a persistent infection results in rupture of the eardrum.
Ear infections are the No. 1 reason for veterinary visits in one pet insurance company’s review of nearly a half million claims. A particular kind — yeast infections — is extremely common in dogs, but the term is actually imprecise, according to dermatologist Lowell Ackerman, DVM, adjunct professor of clinical medicine at Cummings School of Veterinary Medicine at Tufts University.
Many healthy dogs have some yeast on their bodies. The most common, Malassezia pachydermatis, is present on the skin and mucous membranes of many healthy dogs, Dr. Ackerman says. “Typically, there needs to be an underlying problem that creates an environment on the skin or in the ear canals that is conducive to the overgrowth of these yeasts.”
Humans can also acquire yeast-related problems. “But the type of yeast infection seen in people, Candida albicans, is rarely seen in dogs,” says Dr. Ackerman.
Sometimes the terms “yeast infection” and “fungal infection” are used interchangeably, but Dr. Ackerman says the usage is inaccurate. “True fungi cause clinical signs that can be classified as superficial (for example, ringworm infection of the skin), intermediate (for example, aspergillosis infection of the nasal cavity) or deep/systemic (for example, blastomycosis infection of bones and other tissues). But there’s really just one common type of yeast infection in dogs.”
Yeast overgrowth does not usually occur spontaneously. An underlying condition, such as an allergy or the skin disease seborrhea, opens the door for the overgrowth to develop. “For example, allergens cause inflammation, and the inflammation disrupts the normal defense mechanisms of the skin,” says Dr. Ackerman. “This leads to the yeast overgrowth.”
Any allergen can trigger the overgrowth, including pollens, molds, housemites, parasites such as fleas and even certain foods.
Similarly, seborrhea causes scales to form on the skin, including that of the ear, as well as triggering excessive greasiness of the skin and hair coat. Any dog can develop the condition, but cocker spaniels, springer spaniels, basset hounds, West Highland white terriers, Labrador retrievers, golden retrievers and German shepherd dogs are among the breeds most affected. The condition also often causes inflammation and itchiness.
In addition to odor, the signs of yeast infection include:
– A discharge from the ear canal
– Repeated head shaking
– Frequent rubbing of the head and ears on the ground or a vertical surface such as furniture
– Redness and/or inflammation of the ear canal
– Redness and/or inflammation of the skin of the pinna (ear flap)
– Unusual odor from the ears
– Repeated scratching of the ears
Any of these signs should prompt a veterinary examination and the start of treatment.
One popular misconception regarding yeast overgrowth is that dogs with floppy ears are more likely to experience the condition than dogs with upright ears. “Yeast overgrowth is more a function of inflammation than air circulation,” Dr. Ackerman says. “However, many breeds with floppy ears may have yeast overgrowth because they also have allergies and/or seborrhea.”
If the veterinarian suspects that a yeast overgrowth is causing ear problems, he may swab the dog’s ear to collect a sample of any discharge. He’ll then view the sample under a microscope. If the sample shows a higher than normal level of yeast, the diagnosis is confirmed.
Treating a yeast overgrowth effectively usually requires a two-track approach, especially if the current condition is a recurrence. The first track aims at reducing the dog’s discomfort and bringing the yeast level back to normal — often, says Dr. Ackerman, with a combination of oral and topical medications.
The topicals may include a commercial ear cleaner that contains acetic acid, boric acid or benzoic acid to make the ear canal more acidic and inhospitable to yeasts. That’s often followed by topical antifungal ingredients such as nystatin, clotrimazole or miconazole, alone or in combination with antibiotics and anti-inflammatory agents.
The veterinarian may also prescribe an oral antifungal agent effective against yeasts, such as ketoconazole, fluconazole or terbinafine. Even though yeast is technically not a fungi, it may respond to antifungal medications. Treatment generally causes the dog’s clinical signs to begin subsiding in a few days, but it’s important to continue using the remedies for as long as the veterinarian specifies.
While these topical and oral medications can control yeast, an overgrowth often will recur unless the underlying cause is found. This is where the second track of the approach comes in: conducting tests to discover, if possible, the trigger for the overgrowth in the first place.
If food allergies are suspected, the veterinarian will suggest a food trial, also known as an elimination diet. The dog is fed a very simple diet consisting of one protein and one starch that he’s never had before. Treats, oral medications and supplements are prohibited for the duration of the trial. If the dog’s signs subside in four months or less, foods in his pre-trial diet can be reintroduced, one at a time, until the allergic reaction is retriggered. Any food that triggers a reaction is banned from the dog’s diet.
Testing for allergies
When the food trial doesn’t uncover an allergen, testing for other allergens may be necessary. The tests can be performed through a blood sample or injections into the skin. If the dog’s clinical signs tend to occur only at certain times of year — for example, during the same month every year — seasonal allergies to substances such as tree pollen, grass pollen or weed pollen might be suspected.
For certain allergens, treatment can include avoidance to the degree possible. For example, if mold is found to be a trigger, keeping the dog out of the basement will be recommended. Other treatments could be topical medications and immunotherapy — allergy shots. They’re effective about 75 percent of the time but may take up to a year to be effective.
Treating yeast overgrowth and preventing recurrence can be tedious, time-consuming and often frustrating. However, the effort is worthwhile. Successful management of the condition helps free dogs from chronic, often miserable ear itchiness and pain. Failure means that, “They’ll get progressively worse because of more inflammation and may become further complicated with bacterial infections,” Dr. Ackerman says.
Ridding your dog of that yeast-like odor from his ears is an investment in improving his long-term health and quality of life.
Susan McCullough is a writer in Lakewood Ranch, Fla.