There is a lot of mythology out there about food allergies. The recent concern about the potential risks of grain-free diets is only an issue at all because such diets became wildly popular with no evidence that grains were a problem in the first place. A lot of folks blame grains for allergies and other health problems, but there’s no real evidence this is true, and these ingredients probably play a fairly minor role in food allergies in dogs and cats.
Other myths about food allergies include the idea that changing diets can cause them (actually, prolonged exposure is usually needed to develop a sensitivity), that raw foods are less allergenic (nope, only more likely to give you a food-borne illness), and that you can use blood, hair, or saliva tests to diagnose food allergies (sorry, a limited ingredient diet trial is the only way to do this). This last misconception is perpetuated despite evidence from human medicine that it is not true because, quite frankly, it makes people money.
I’ve previously discussed an example of this quackery, Jean Dodds’ Nutriscan allergy testing system. In her book, Dr. Dodds provides many citations to support her claim that this is a legitimate test, but a cursory look at these shows they don’t make that case at all. And there are unpublished reports from at least one allergy specialist that suggest the test is not merely inaccurate but completely useless nonsense:
One veterinary dermatologist has performed her own uncontrolled test of Nutriscan, with Dr. Dodds’ knowledge and permission, and found it entirely unreliable. Twelve samples were submitted for testing in a blind manner, from dogs with known food sensitivities based on dietary testing, dogs with environmental allergies, dogs without allergic disease, and one sample of tap water. All samples including tap water, environmental allergy dogs, and normal dogs showed reactivity to beef, corn, milk and wheat. Some samples showed reactivity to soy. In some cases, these obviously false results would have led to recommendations against diets which actually helped these dogs.
Granted, this is essentially an unpublished anecdote, so while it counters the anecdotes Dodds and others put forward for Nutriscan, it is not published scientific research. Now, however, a different allergy test, using saliva and hair samples to identify allergies, has failed the same test as spectacularly as Nutriscan purportedly did.
Coyner K, Schick A. Hair and saliva test fails to identify allergies in dogs. J Small Anim Pract. October 2018. doi:10.1111/jsap.12952
Our study demonstrates that hair and saliva testing fails not only to identify allergic dermatitis in dogs, but fails to differentiate between animal and non-animal samples, providing essentially identical results, regardless of the origin of the sample.
These authors submitted not only hair and saliva from dogs with known allergies and dogs without allergies, but also fake hair samples from stuffed animals and water (in place of saliva). All of the samples tested positive for some allergies, and there was essentially no difference between the results and random chance.
Saliva and hair tests for food allergies are a scam and a waste of time and money.