Allergy Tests for Pets
Written by: Tracy Vogel, Staff Writer @ Vetcentric.com

When people have allergies, the usual symptoms are congestion, sneezing, itchy eyes, and runny noses.

When pets have allergies, they itch. Your dog and cat can be allergic to dust mites, ragweed and fungal spores -- just like you -- but they show it differently.

Atopic dermatitis -- the animal equivalent of hay fever, is an "unbelievably complex disease," said Dr. Andrew Hillier, assistant professor of dermatology at Ohio State University's College of Veterinary Medicine. "It's not a disease easily cured."

Two main tests are used for possible allergy patients. One is the skin test, in which substances are injected into the skin to determine allergic reaction. The second is a serum test, in which blood serum is sent to a laboratory and exposed to various allergens to determine reaction.

The serum test is the more recent technology. Companies are working to refine the test -- one company, Allercept, has gone as far as to isolate the cell receptor that reacts to the production of antibodies that bind to the cells.

The receptors, along with a colored marker, are used to determine whether the blood serum contains those elevated levels of antibodies, thus indicating a possible allergy.

"It's an extremely specific test because it doesn't cross-react with other antibodies," said Dr. Rebecca Turnbull, a marketing manager and veterinarian.

The company also aims for preciseness in detecting the allergens. To look for flea sensitivity, scientists use flea saliva -- the element that causes the allergy. Flea farms are fed blood covered by a membrane. When the insects bite through the layer, the membrane collects their saliva.

The saliva is placed in a small section of a tray. Other potential allergens are placed in additional sections. The serum, receptor, and marker are added to the tray. If a reaction occurs, it indicates a sensitivity to the substance.

But allergy tests are only part of the picture, Dr. Hillier warned. "These are not tests of allergy," he said. "They're tests of hypersensitivity."

An animal can be hypersensitive to a variety of allergens without being allergic -- a dog can be hypersensitive to dust mites, for instance, but not experience allergies.

Dr. Turnbull also emphasizes that her company's test doesn't diagnose allergies -- it only detects the presence of the elevated antibodies after the veterinarian has already determined that the pet is allergic. "If they've done the work they should, it's very useful," she said. "One of the keys to proper diagnosis is a thorough history."

So it's essential to rule out the other causes of disease, Dr. Hillier said. Flea allergies, for example, are easy to rule out, as are scabies and food allergies.

Then the veterinarian should conduct the skin or serum test. Dr. Hillier uses both the serum test and skin test for his patients. Often the results correlate, but sometimes they don't, and it's best to have as much information as possible, he said.

Given only one choice, he said he would do a skin test, simply because he has the equipment for it. Without a skin test kit, he would go for the serum test. But he expects both to be around for the foreseeable future. "Both have faults and advantages."

Dr. Thierry Olivry, a professor at the North Carolina College of Veterinary Medicine, Raleigh, N.C., also uses both tests -- but only if the client is willing to put the pet through immunotherapy. "They may not be measuring exactly the same things," he said.

Neither test is effective for detecting food allergies.

After the serum and skin test, veterinarians need to look at the results again, in the context of the animal's medical history, Dr. Hillier said.

For instance, tests show a reaction to the household dust mite, which causes year-round allergic reaction. But the animal only shows symptoms in spring and summer. "It makes me look back û do we have good flea control," Dr. Hillier said. "Mosquitoes or flies are more likely to cause irritation in spring and summer."

Or perhaps the results say the dog is hypersensitive to seven different trees, and eight grasses. If the dog has year-round disease -- including in the winter, when trees and grasses don't come into play -- that indicates that while flora may be contributing to the symptoms, it doesn't explain the source of the allergy entirely.

From there, it's a matter of determining treatment, which breaks down into three categories. Owners can avoid exposing the pet to the allergen, vaccinate against it, or treat the symptoms.

Too often people leap to treating the symptoms -- using special shampoos, antihistamines, anti-inflamatories, and so on -- before trying to identify the allergen, Dr. Hillier said.

That works for a while, but eventually the medications may stop working on that pet, or the condition worsens. So it's best to find the cause of the problem, if possible, Dr. Hillier said.

The vaccination is actually immunotherapy. Once veterinarians determine what allergens affect the pet, they come up with a solution containing those elements. The solution is injected into the pet, first every other day, then every two weeks, over a course of a few months, Dr. Olivry said.

Eventually, the animal may become desensitized. The therapy is effective in 60 to 80 percent of patients, he said. However, treatment is usually long-term, if not life-long.

Jeffrey Adler of Gainesville, Fla., went through the long process of identifying the triggering allergen for his young dog, which was suffering from hot spots and ear infections.

Veterinarians did a skin test and studied the dog's history. In Dr. Adler's case, the dog turned out not to be allergic to airborne substances -- it had food allergies.

"Once the dermatologist identified the basis for the allergies, they put [the dog] on a prescription diet," he said. "We've gone two to three years without any problems -- they identified the problem and came up with a solution."

*Article courtesy of VetCentric.com
Originally published June 2, 2007
Written by: Tracy Vogel, Staff Writer
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