Another in-vitro test for dog skin allergies is called the ELISA (enzyme linked immunosorbant assay) test.
The Rast test is often a more expensive but potentially more accurate test for a dog allergy.
The RAST tests for the levels of allergen specific IgE.
The reason why they are looking for a specific antibody within your dog is that when an allergen such as a pollen particle enters the dog body for the first time it stimulates the body to produce antibodies. A BIG reaction is the beginning of sensitization that in allergy prone dogs just gets stronger and stronger each season (if allergic to a seasonal allergen like pollen).
The class of antibodies related to allergies is called IgE (immunoglobulin E). The reason that the body creates the IgE antibody is that it is part of the body’s natural protection mechanism – it literally attaches to the allergen in order to neutralize it. Its just that when a body accidentally identifies something like pollen as a serious threat and goes out of control to kill it, you produce the severe unnecessary allergy reactions.
Benefits in rast tests for dog allergy testing
While more expensive and not able to identify specific allergies like the intradermal testing discoursed in the previous article, this test will give a qualitative (number) result for the level of dog allergy for whatever allergen is going to be identified by the rast test. Usually there are dozens of common household and dog park allergens that the rast test will give you a specific sensitivity number to (versus the normal range for that allergen)
And while it does draw blood, it is much less invasive than putting a matrix of potential allergens under the dogs skin as in the intradermal test. It also doesn’t need for the dog to be free of cortisone, tranquilizers or any other drug. The igE level will be detected regardless of the other drugs in the dog’s system.
DOWNSIDE – like many blood tests false positives can occur. You need to understand teh confidence interval of the statistics of this test to understand how reliable it is.
the RAST Test and food allergy testing
Ironically most dog allergy papers and sites will tell you that the only true method of testing for a food allergy is the exclusion diet where a dog is given rare bland food to see if it results in them recovering from allergy symptoms . BUT the RAST test can also give numerical sensitivity values for specific foods such as soy, eggs, milk, beef, venison chicken etc.
While the rast test will give you a number for a believed allergen, it is still only a guide. The process usually is that a intra-dermal AND rast test can identify what meat of veggie source is MOST LIKELY the cause of an allergy, then it is CONFIRMED via an exclusion diet.
This give us a rough idea of what food your pet might be allergic to, and can only be confirmed with the trial elimination diet.