Updated July 2023
Diagnosing food allergies or ruling them out completely has always been a frustrating and time-consuming endeavour. The traditional way to diagnose food allergies in dogs is through an elimination diet, but this process can take months.
As a result, many dog owners and vets reach for simpler methods and test for allergies in their dog’s blood or saliva. But are these tests any good? Can blood and saliva tests accurately diagnose a food allergy in your dog?
How do blood and saliva tests work?
Blood tests work by measuring the immune response to particular foods by detecting antibodies. Specifically, they measure a class of antibody called immunoglobulin E – commonly linked to allergic reactions.
After the sample is taken and sent to a lab, a common lab technique called an ELISA is used. In this case, the food-specific allergen that you are testing for are stuck to plates in a lab. Next your sample is added and if it contains the right antibodies, they will bind to the allergen. If there are any antibodies that have stuck to the antigen, there will be a colour change in the plates, indicating a positive test. Negative tests would not show any colour changes.
Saliva tests also test for antibodies that would hunt down and bind to specific food allergens – the substances that cause the allergic reaction. However, in this case, these tests look for different classes of antibodies called immunoglobulin A or immunoglobulin M.
How accurate are these tests?
Previously, we didn’t have much data to show how effective these tests were to accurately identify allergens, but that has changed in recent years with new research. So, let’s take a closer look.
In a European study researchers compared a popular saliva test and a popular blood test in three groups of dogs:
● Healthy dogs with no allergy symptoms
● Dogs with suspected food allergies
● Dogs with known food allergies
The results came back showing more positive reactions to food allergens in the healthy dogs than the dogs who had already been diagnosed with an allergy. Only one of the positive blood tests corresponded to a known allergy in one of the allergic dogs.
A second study, which was done in US, used a saliva test and two blood tests on a group of healthy dogs with no evidence of allergies. All the dogs tested positive in at least one of the tests, sometimes for a number of different common food allergens.
One readily available hair and saliva allergen test even failed to recognise fake hair and fake saliva that had been submitted for testing by a group of researchers. Furthermore, the testing company provided positive test results towards particular allergens and triggers for all submitted samples – including the synthetic fur and saline!
More harm than good?
There is no evidence to support that performing these tests are harmful. However, there are many ways that these tests could do more harm than good.
Firstly, the false identification of an allergy may lead to dog owners eliminating a variety of foods unnecessarily or even buying more expensive and uncommon foods that could pose other risks.
And in some cases, these false results may lead to recommendations against diets which actually would have helped these dogs.
Take-away for dog owners
In short, save your time and your money!
While it may be tempting to use hair, fur or saliva tests to identify your dog’s allergies, it is vital to remember that these tests aren’t accurate, and the results provided can be very misleading. There isn’t any evidence that suggests they can identify a healthy dog from one with allergies. The best steps when confronted with a possible food allergy is to:
1. rule out other conditions,
2. identify trigger foods via an elimination diet, and
3. get support from a dietetic professional