Allergy Tests for Dogs

What is hyposensitization treatment for dogs?

Hyposensitization treatment involves giving your dog a small amount of the allergen trigger by mouth or as injections every one to four weeks. Exposing the dog’s immune system to small quantities of the allergen can stimulate an immune response that can lead to a build-up of immune tolerance. About 60-80% of dogs experience improvement with hyposensitization.

How to Prepare Your Pet for Allergy Testing

Since certain medications can interfere with testing and may alter test results, you should inform your vet about all the medications and supplements that your pet may be taking. Some of the medications that must be avoided before testing include:

• Cortisone medications including cortisone lotions - stop giving these medications to your pet at least 2-4 weeks before testing.
• Antihistamine pills - must be stopped at least 7 days before an allergy test.
• The vet or the veterinary staff may also inform you if there is a need to withhold food and/or water to the pet on the night before testing. If you’re uncertain, don’t hesitate to call your vet.

Types of Allergy Testing in Dogs

Veterinarians usually recommend allergy testing after eliminating other potential causes. Before an allergy test is performed, your vet will check your dog for external skin parasites or infections by conducting certain diagnostic tests to determine if any of these factors are behind your dog’s allergies. Once these potential causes have been ruled out, your vet may discuss testing for specific allergens.

Two techniques can be used for allergy testing in dogs: intradermal skin testing and RAST testing.

Intradermal Skin Testing

Intradermal testing is regarded as the gold standard in identifying the allergen that is causing atopic dermatitis in dogs. The test is performed only by veterinary dermatologists, thus there is a need for dog owners to seek one in order to have their dogs tested. Unfortunately, veterinary dermatologists may not be available in certain areas and travel can mean additional expenses. Also, intradermal skin testing requires a dog to be given anesthesia. Large areas of the hair coat must be shaved to make it easier to monitor the injection sites.

How Intradermal Testing Is Performed

The test involves administering about 60 injections just under the dog’s skin. If the pet is allergic, there will be a hive-like reaction on one or more injection sites. Intradermal tests are more expensive than blood testing, but it is much more accurate than other options.

RAST Test (Blood Test)

The Radioallergosorbent test (RAST) is used to identify certain allergens that a dog may be allergic to. The blood test is one of the procedures that are performed when diagnosing atopy (inhalant allergy) in dogs.

Atopy or atopic dermatitis is a hypersensitivity reaction to allergens that are airborne and inhaled by dogs. Many cases of atopy are seasonal allergies that are manifested by skin redness and itching. Intense itching and persistent scratching can cause breaks in the skin surface that can eventually create a favorable environment for secondary skin infections.

RAST is performed using only one blood sample obtained from the dog. Your vet can draw the blood during your dog’s wellness visit and submit the sample to a laboratory for analysis. With RAST, there is no need to have your dog sedated or anesthetized. Also, shaving your dog’s hair is not needed.

While the blood test is less expensive than an intradermal test, the results require more careful interpretation. There is also the issue of human error, meaning, laboratories may have varying results.

Should I stop giving allergy medications to my dog before RAST Testing?

There is no need to stop giving allergy medications to your dog before RAST testing. However, this is not the case with intradermal testing, which usually requires that dogs be taken off allergy medication for a significant length of time before the test is performed.

Drawbacks of RAST Testing

Compared to intradermal testing, there is an issue of a higher rate of false-positive test results with RAST testing. Also, there are positive RAST results that cannot be confirmed when intradermal skin testing is performed.

However, there is still a significant improvement in skin allergy cases in dogs when treated with hyposensitization based on the results of RAST testing.

RAST Takeaway

Pet owners should understand that RAST Testing is only recommended if there is a plan to have allergic dogs undergo hyposensitization treatment. The test should not be used to solely diagnose atopic dermatitis. It is only used to identify the allergen culprit of atopic dermatitis that has already been diagnosed.

Considering that the allergens associated with atopy include a wide variety of trees, flowers, weeds, and other environmental allergens, it’s impossible to avoid a dog’s exposure to them. The true benefit of RAST Testing is in obtaining results that can serve as a guide in the formulation of a treatment regimen that involves hyposensitization therapy.

Pet owners should understand that no allergy test is 100% reliable in pinpointing the culprit of allergies in dogs. Neither intradermal skin testing nor RAST testing is consistently better. In many cases, veterinarians recommend both tests to get the most information about the allergic sensitivities of the patient.

Read more:

Food Allergies in Dogs and Cats

Ditch the Itch: Skin Allergies in Dogs

Common Ear Problems in Dogs

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