A prospective double-blinded study evaluating threshold doses of dietary allergens that trigger adverse food reactions in dogs, and time to flare after exposure.

Introduction: Adverse food reactions (AFR) are a common cause of chronic pruritus in dogs and often present as atopic dermatitis. However, the threshold dose of dietary protein required to trigger clinical signs of AFR, as well as the time to onset of those signs, remain poorly defined. Methods: This prospective, double-blinded study aimed to determine the approximate dose of food protein required to elicit clinical signs in dogs with previously confirmed AFRs and to assess the time to flare (TTF) following a single dietary protein provocation. Eleven dogs with confirmed AFR underwent 71 randomized oral food challenges (OFC) with seven individual protein sources in escalating doses for each protein over 7 days. Results: Clinical signs were observed in 35 challenges, most commonly between days 2 and 6, with a mean TTF of 4.1 days (range: 1-7 days). Reactions were mostly triggered by 20-30 g of food protein, with a mean dose of 21 g (range: 1-30 g). When adjusted for body weight, this corresponded to a median eliciting dose of approximately 0.86 g/kg (range: 0.06-2.5 g/kg). Discussion: While most dogs reacted to moderate-to-high protein exposure after repeated OFC, the variability in individual responses in both threshold dose and TTF highlights the need for further studies to refine diagnostic protocols and define clinically relevant threshold doses.