While cutaneous signs are common in adverse food reactions, a subset of animals may present without pruritus, skin lesions, or other dermatologic manifestations. A 2018 metanalysis revealed that among internists, nearly 75% of dogs and 50% of cats presented with GI signs alone yet were highly suspected of having adverse food reaction supported by clinical findings and empirical improvement. These findings suggest it is critical to assess for AFR early in the workup of gastrointestinal signs, particularly prior to pursuing more invasive and costly diagnostics.

Source: Mueller RS, Olivry T. Critically appraised topic on adverse food reactions of companion animals (6): prevalence of noncutaneous manifestations of adverse food reactions in dogs and cats. BMC Vet Res. 2018 Nov 12;14(1):341. doi: 10.1186/s12917-018-1656-0. PMID: 30419909; PMCID: PMC6233561.

In a recent metanalysis, the top allergens contributing to cutaneous adverse food reactions in dogs included beef, dairy, chicken, wheat, and lamb. Beef, fish, and chicken topped the list in cats.

Source: Mueller RS, Olivry T, Prélaud P. Critically appraised topic on adverse food reactions of companion animals (2): common food allergen sources in dogs and cats. BMC Vet Res. 2016 Jan 12;12:9. doi: 10.1186/s12917-016-0633-8. PMID: 26753610; PMCID: PMC4710035.

While these methods may be useful for assessing environmental atopy, their reliability for diagnosing adverse food reactions (AFRs) is low, and may inadvertently prolong the trial phase and frustrate the client. While additional modalities may be used for academic purposes, a proper elimination trial remains the most reliable and veterinary dermatologist recommended method for diagnosis of AFRs.

Source: 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 Aug 30;13(1):275. doi: 10.1186/s12917-017-1142-0. PMID: 28854915; PMCID: PMC5577833.

While avoiding triggering allergens through elimination trials or novel protein diets may lead to clinical improvement, studies show that over 50% of dogs allergic to intact proteins have clinically improved when fed foods with protein hydrosylates, which are processed to reduce polypetide size to below the theoretical threshold for immune detection. Important factors to consider when selecting a hydrolyzed diet include both the mean molecular peptide size, measured in daltons, as well as the percent of these peptides below the theoretical threshold of 10,000 daltons. Selecting a diet whose protein source is not considered a common allergen may also aid in clinical improvement, since even a small percentage of peptides above the immune detection threshold may lead to ongoing clinical signs.

Blue Buffalo NVD HF features hydrolyzed salmon as its only animal protein source, with a mean molecular weight of 2,000 daltons and 97.3% of peptides below 10,000 daltons.

Sources: Jackson HA. Food allergy in dogs—clinical signs and diagnosis. Eur J Comp Anim Pract. 19: 230-233, 2009.

Gaschen FP, Merchant SR. Adverse food reactions in dogs and cats. Vet Clin North Am Small Anim Pract 41:361-379, 2011.

Roudebush P, Guilford WG, Jackson HA. Adverse reactions to food. In Hand MS, Thatcher CD, Remillard RL, et al. (eds): Small Animal Clinical Nutrition, 5th ed, Topeka, Kan, 2010, Mark Morris Institute, p 609.

While thorough cleanouts and high heat sanitation of manufacturing lines are industry standard in the creation of veterinary allergy diets, some manufacturers employ additional molecular testing to ensure no evidence of contaminating proteins. For example, Blue Buffalo NVD HF undergoes ELISA testing on both base ingredients and finished diets to ensure there is no evidence of contaminating chicken, egg, beef, or soy. Blue Buffalo NVD NP undergoes this same ELISA testing, plus PCR evaluation for chicken protein. Be sure to ask your food manufacturer representative what methodologies are employed to ensure no contaminating proteins.