Ask the Vet | Allergy Blood Test for Dogs

Allergies are some of the most common skin conditions we have to deal with in daily practice here in Macau. It seems as if most dogs that come from other countries into Asia, especially HK and Macau, seem to develop some sort of contact or food allergy.
Allergies can be suspected if the dog has symptoms such as sneezing, runny nose, watery eyes and itchy skin. To confirm the diagnosis, tests must be performed. Allergies may be diagnosed through skin tests, blood tests, elimination tests and food trials. An allergy blood test may be used if the dog is suspected of having inhalant allergies.

Blood Tests for Allergy Testing

The blood tests are most commonly used to diagnose allergies if the vet suspects inhalant allergies. There are two blood tests that can be used in canines to detect allergies. The vet will extract a blood sample and perform the test on the sample. The two tests are the RAST (radioallergosorbent) testand the ELISA (enzyme linked immunosorbent assay) test. These are both similar in methodology, but the ELISA test is considered superior, giving more accurate results.
RAST Test
The RAST test will be performed on a blood sample, which should contain an allergen specific antibody, should the dog be allergic to any possible allergens. The antibody will point to the exact substance the dog is allergic to. The test can be performed at any time and the results will be available in one or two days.

ELISA Test
The ELISA test is very similar to the RAST test and will also reveal the presence of certain antibodies, if the dog is allergic. The ELISA test is pricier, but it is said to give more accurate results.

Disadvantages of Blood Test for Allergy Testing
The blood tests performed to detect allergies in dogs may only be used to detect inhalant allergies or parasite allergies. If the dog is suspected of contact allergies or food allergies, the blood tests will not show any conclusive results. In these cases, elimination trials are necessary.
Another disadvantage is that there are certain antibodies that are not yet identified and are secreted in reaction to different lesser known allergens. Consequently, the test may not isolate the exact allergen and additional tests may be required.

Alternative Allergy Testing
The allergies may also be detected by using one of the following procedures:
• Intradermal testing, which will require the dog to be injected with different suspected allergens. This may not be effective if the allergen is rare. Intradermal testing cannot detect food or contact allergies, but it is believed to be more efficient than blood testing in diagnosing inhalant allergies.
• Food trials are only used if the dog is suspected to have food intolerance and displays symptomsthat involve the gastrointestinal system. The trials may be time consuming and the allergen may not be detected.
• Elimination tests are used if the dog is suspected to have contact allergies and blood testing is not possible or hasn’t given conclusive results. The tests will involve removing one suspected allergen at a time from the dog’s environment and waiting for up to two weeks to monitor the dog’s reactions.

Hope this helps
Till next week,
Dr Ruan

Ask the Vet:
Royal Veterinary Centre
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