Adverse food reaction is defined as an abnormal response to ingestion of food or food additive and may be a food intolerance or a food allergy, while a food allergy is an immune mediated response to a food antigen, typically a protein in the food.
Unfortunately, food allergy testing via serum or saliva for dogs/cats has not been confirmed to be diagnostic at this time, and results will often unnecessarily exclude ingredients while failing to identify true food allergens.1-3,8 This can be frustrating and complicate choosing appropriate ingredients in a homemade recipe of a commercial food for a diet trial. Ideally “novel” ingredients should be selected – these are ingredients that have not been fed prior. At minimum, they should not have been fed regularly when symptoms occurred. Novel ingredients are unlikely to be food allergens as the immune system has not been exposed to them. Novel protein ingredient(s) (but sometimes also novel carbohydrates) are chosen by reviewing the full diet history for each individual pet. For dogs with numerous protein exposures, hydrolyzed protein diets may be the best choice for a feeding trial. Hydrolyzed proteins are proteins that are broken down into very small, non-allergenic sizes. Diets containing hydrolyzed proteins are only available in therapeutic (prescription) commercial foods. Hydrolyzed diets also work well as a diagnostic test to confirm if food allergy is present.
A Hypoallergenic Food Trial should last for a minimum period of 12 weeks for dogs with symptoms affecting the skin during which no other food items should be fed except for approved treats (these should be similar in ingredients or contain hydrolyzed protein). Skin symptoms may improve after 12 weeks or more, while gastrointestinal symptoms often improve faster, perhaps within 2-3 weeks of feeding. Diet trials for gastrointestinal concerns should last at least 8 weeks to confirm the food is well tolerated.
The following are current statistics reported by recent literature concerning incidence of food allergies in dogs1,4-8:
Prevalence of adverse food reactions for dogs:1,5-8
For all dogs seen: 1-2%
Dogs with skin disease: 0-24% = dogs with pruritis (itchy skin): 9-40%, any allergic skin disease: 8-62%: dogs with atopic (environmental) dermatitis – 9-50%
Sources of Food Allergens for dogs:1,5-8 database searched 1985-2015, studies pulled where offending allergens identified and positively confirmed on re-challenge; North America, Australia, Europe
Dogs: beef (34%), dairy (17%) chicken (15%), wheat (13%), soy (6%), lamb (5%)
Less common: corn (4%), egg (4%), pork (2%), fish (2%), rice (2%)
Very rare: barley, rabbit, chocolate, kidney bean
Cross-reactivity between foods can occur and should be considered. It may be difficult to determine whether clinical signs associated with itchy skin (pruritis) and/or secondary skin infection are caused by food allergy (less common) versus environmental allergies (much more common) or a combination of the two in the same patient. Secondary skin infections with bacteria and/or yeast must be treated and cleared to avoid continuation of signs despite appropriate medical or dietary therapy.
Food allergy can only reliably be diagnosed via a positive clinical response to an elimination diet trial (typically lasting 8-12 weeks), then a subsequent relapse of clinical signs with diet provocation (usually within 2 weeks).
- Mueller RS, Olivry T. Critically appraised topic on adverse food reactions of companion animals (4): can we diagnose adverse food reactions in dogs and cats with in vivo or in vitro tests? BMC Vet Res. 2017;13(1):275.
- Coyner K, Schick A. Hair and saliva test fails to identify allergies in dogs. J Small Anim Pract. 2019;60(2):121-5.
- Udraite Vovk L, Watson A, Dodds WJ, Klinger CJ, Classen J, Mueller RS. Testing for food-specific antibodies in saliva and blood of food allergic and healthy dogs. Vet J. 2019;245:1-6.
- Hillier A, Griffin CE. The ACVD task force on canine atopic dermatitis (X): is there a relationship between canine atopic dermatitis and cutaneous adverse food reactions? Veterinary immunology and immunopathology. 2001;81(3-4):227-31.
- Olivry T, Mueller RS. Critically appraised topic on adverse food reactions of companion animals (3): prevalence of cutaneous adverse food reactions in dogs and cats. BMC Vet Res. 2017;13(1):51.
- Olivry T, Mueller RS. Critically appraised topic on adverse food reactions of companion animals (5): discrepancies between ingredients and labeling in commercial pet foods. BMC Vet Res. 2018;14(1):24.
- Olivry T, Mueller RS. Critically appraised topic on adverse food reactions of companion animals (7): signalment and cutaneous manifestations of dogs and cats with adverse food reactions. BMC Vet Res. 2019;15(1):140.
- Lam ATH, Johnson LN, Heinze CR. Assessment of the clinical accuracy of serum and saliva assays for identification of adverse food reaction in dogs without clinical signs of disease. J Am Vet Med Assoc. 2019 Oct 1;255(7):812-816. doi: 10.2460/javma.255.7.812. PMID: 31517577.