Pet Talk: Dogs' itchiness might indicate atopic dermatitis
By Sarah Netherton/University of Illinois College of Veterinary Medicine
Like people, pets suffer from allergies. Sometimes, these allergies are triggered by items commonly found in the pets' environment, such as pollens, mold, house dust, kapok (used as filling in pillows and cushions), sawdust, human dander and feathers, just to name a few.
Karen Campbell, a veterinarian at the UI Veterinary Teaching Hospital in Urbana who is board certified in both internal medicine and dermatology, says that atopic dermatitis is a condition in which the immune system reacts too strongly or inappropriately to common environmental allergens that are absorbed through the skin. (The term atopic derives from the Greek word for out of the way or unusual.)
"Between 10 percent and 15 percent of the dog population has atopic dermatitis," Campbell said, "making it second only to flea allergy dermatitis in the number of dogs affected. These animals suffer from a dysfunction in their skin barrier that increases the absorption of allergens and decreases resistance to secondary infections."
The skin is the body's first responder against infection, and animals whose innate protection in the skin is compromised are more susceptible to skin infections. Signs of atopic dermatitis include scratching, hair loss, redness of the skin, sores, skin that is thick and leathery due to scratching and skin that is flaky. The itching and rashes typically affect the face, ears, legs, feet, armpits and groin region.
Owners also may notice their pets sneezing and sweating. Inflammation of the lining of the eyelids (conjunctivitis) is another condition associated with atopic dermatitis.
To diagnose atopic dermatitis, veterinarians consider the type and distribution of the rashes, the breed of dog and whether the condition appears to be seasonal or chronic. The age of onset also is an important diagnostic clue.
"In about 75 percent of affected dogs, the signs first arise between 6 months and 3 years of age," Campbell said. "It is rare for onset to occur in dogs over 7 years of age, unless the pet has moved to a new environment in which there are new allergens."
Breeds that are genetically predisposed to this condition include terriers, beagles, Irish and English setters, Lhasa Apsos, pugs, English bulldogs, miniature schnauzers, Labradors and golden retrievers.
Atopic dermatitis can be seasonal. According to Campbell, most dogs begin to show signs between the spring and fall months. About three-quarters of affected dogs will be afflicted year-round.
A blood test to determine the presence of an antibody called IgE to specific allergens may help with the diagnosis. An increase in allergen-specific IgE usually means there is an overreaction of the body to that allergen.
Veterinarians also can perform a skin test on a patient with suspected atopic dermatitis to help identify the allergen associated with the disease so that the appropriate treatment can be provided, although a skin test alone does not give a definitive diagnosis of atopy.
"In trying to figure out the cause of the allergy, a veterinarian also must rule out external parasites, such as fleas or demodex (a mite that causes mange); a food allergy; or inflammatory disorders such as an infection, dry skin or some other irritant that is causing the itching," Campbell said.
Once the specific allergen has been determined, the appropriate treatment can begin. Avoiding the allergen may not be practical in some situations, but for dogs that are allergic to cottonseed, for example, keeping them off mattresses and upholstery would be beneficial.
Because the allergens are absorbed through the skin, giving an affected dog a weekly bath to wash off any allergens on the skin also may be helpful.
If avoiding the allergen and bathing the animal are not providing relief, a veterinarian can prescribe medications to control the itchiness or might recommend immunotherapy, a series of shots that desensitize the animal to the allergen.
An archive of pet columns from the UI College of Veterinary Medicine is available at http://vetmed.illinois.edu/petcolumns/. Requests for reprints of this article may be directed to Chris Beuoy, firstname.lastname@example.org.