In 2010, I reported on the evidence-based guidelines for treatment of allergies in dogs put out by the International Task Force on Canine Atopic Dermatitis. This extremely useful document reviewed the evidence concerning many different treatments for allergies in dogs, from topical shampoos and medications to oral medications and dietary supplements. While the lack of evidence for particular therapies does not always mean these treatments don’t work (though this can indicate a lack of efficacy under certain circumstances), it makes sense to focus our efforts on those treatments that have the best chance of helping our itchy canine companions, and these are the treatments that have built up a strong foundation of scientific evidence, from basic lab testing through clinical trials. The task force report helps us to know which treatments those are.
Olivry, T. et al. Treatment of canine atopic dermatitis: 2015 updated guidelines from the International Committee on Allergic Diseases of Animals (ICADA). BMC Veterinary Research. 2015;11:210.
The updates to the original guidelines are fairly minor. New research has led to some new treatments, including oral medications topical treatments such as shampoos. Research evidence has also clarified the role of some existing therapies. Some antihistamines, for example, which did not previously have evidence for benefits in itchy dogs now look like they might have some small benefit in mildly effected dogs, especially if given continuously and before a symptom flareup.
The evidence has also grown stronger that “allergy testing” cannot be used to diagnose allergies since positive tests can often be seen in dogs who are itchy for reasons other than allergies. These tests may still be helpful in guiding therapy, though this is not completely clear. There is also still no evidence to support using allergy tests to identify food allergies, though this is still recommended by some vets.
As for dietary supplements, essential fatty acids such as in fish oil are the only one that has any evidence of clinical benefits. What dose, source, or formulation is most effective isn’t known, and there is no clinical evidence for benefit from any other oral supplement.