ALLERGIES IN DOGS
By Leonard D. Jonas, DVM, MS, DACVIM, Wheat Ridge Animal Hospital
Allergies in pets are a very common and often frustrating problem for pet owners. Pets can develop allergies to foods, pollens, medications, airborne molds, fleas, and house dust. Fortunately, the number of pets susceptible to allergies is small; perhaps 10% of all dogs and cats. But for those unfortunate enough to have allergies, they can become very uncomfortable from the itch-scratch cycle that is often difficult to break. The allergic response is an abnormal immune reaction to certain substances in the environment that most other pets tolerate without problems. The itchy skin causes the pet to lick, scratch, and nibble the affected area in a concerted effort to find relief. The symptoms can intensify to include redness, open sores, and hair loss. It is very common for the pets to have flaky and oily skin, which is accompanied by a rancid odor. This condition is called seborrhea. 90% of pets with allergic skin disease will also have an accompanying bacterial or yeast skin infection. The seborrhea, yeast, and bacterial infections contribute to the discomfort associated with the allergic reaction and must be addressed at the same time as the allergy in order to give the pet relief. It is important to remember that not all itching is caused by allergies and that other diseases must be considered when evaluating a pet that is scratching.
There are three types of allergies frequently diagnosed in pets. Fortunately, living in Colorado, we are not often exposed to the most common allergy, flea allergy dermatitis. The second type is allergic inhalant dermatitis. It occurs most frequently in dogs and its symptoms usually develop between the ages of one and three years. Inhalant allergy is the canine version of the human hay fever problem. Afflicted dogs react adversely to allergens such as house dust, molds, and pollens of grasses, trees, and weeds. Unlike human hay fever sufferers, dogs usually develop intensely itchy red skin rather than respiratory symptoms. The third type is food allergy. Dogs and cats can develop an allergy at any time to any type of food. Most commonly it is to corn, wheat, soy, beef, chicken, and/or dairy products. The clinical signs of food allergies are indistinguishable from inhalant allergies.
The majority of dogs with inhalant allergy are sensitive to a number of the airborne allergens, not just one. When they are exposed to the offending allergens, their immune systems react in an abnormal way, causing clinical skin problems. At the onset, a pet’s allergy is often confined to one season when plants and molds are actively releasing their pollens and spores. But, in most cases, over time the allergy becomes chronic with the symptoms lasting year-round. Heredity definitely plays a role in this type of allergy. Genetic susceptibility can be passed from parent to puppy in any breed of dog. Most veterinarians feel that Terriers, Labradors, Golden Retrievers, and Shar Pei’s are especially prone to developing inhalant allergy. Because of the genetic nature of the problem, it is important to understand that allergies cannot be cured but can be controlled.
The dogs with inhalant allergy are usually a paw-licker, face-rubber, and an underarm-and-belly-scratcher. The dog’s skin may be bright pink or red. In some cases, the skin will turn dark brown or black. This color change is not a serious problem in its own right, but it does indicate that the skin irritation has been a long standing problem. It is not uncommon for hair loss, self-inflicted lesions and secondary bacterial infections to occur.
In order to diagnose to which inhalant allergens the pet may be sensitive, intradermal allergy testing is performed. This method has been used for many years with people and animals sus-pected of having inhalant allergies. The procedure involves making small injections in the skin with allergens to which the pet is commonly exposed. If the animal is sensitive to any of the substances, a small red welt will appear at the injection site. The tests are essentially painless and most dogs tolerate them with only mild sedation. Dogs must be off antihistamines for two weeks and steroids for a minimum of two weeks (sometimes longer) prior to testing as these medications will interfere with the test results. In certain circumstances we can use blood testing to assess for inhalant allergies instead of intradermal testing.
When the skin tests have been analyzed, a vaccine can be made for the pet to treat the allergy.
This is called immunotherapy. The pet is given increasing doses of selected mixed antigens, by injection, over a period of months. This alters the immunologic response, which reduces or eliminates the sensitivity to the allergens. The allergens are individually selected for each patient and are based on the results of the skin tests. The owner of the pet is easily trained to give the injections at home. Approximately 75 to 80% of pets that go through the immunotherapy program show improvement with their skin problem. It is important to realize that even with the immunotherapy, other medications will be necessary to control the pets’ allergy symptoms. These include corticosteroids, antihistamines, fatty acid supplementation and cyclosporine. Also antibiotics, anti-yeast medications, and bathing at time of flare-ups will be necessary to control the secondary bacterial and yeast infections and seborrheic problems. In summary, caring for the allergic pet takes a large amount of cooperation and communication between the owner and the veterinarian. This is a major factor in formulating a specific and individualized treatment regimen for each pet. Every patient is different and, therefore, requires a unique combination of control methods. When an owner understands the disease process and his or her pet’s particular problems, it is possible to help the pet live comfortably with the allergy. Conscientious supportive care and a positive attitude can help you control your pet’s allergy and help you break the miserable itch-scratch cycle once and for all.
Dr. Leonard D. Jonas:
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