What is the recommended elimination diet protocol for diagnosing food allergy in a pruritic dog?

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The gold standard for diagnosing cutaneous adverse food reaction (CAFR) in dogs is a 6–12 week elimination diet trial (EDT) using a limited, hypoallergenic protein source, followed by provocation with the original diet. Diagnosis is confirmed when pruritus returns within 14 days of rechallenge. 14 Diet selection is the foundation of a successful trial. Both hydrolyzed salmon (HS) and hydrolyzed poultry feather (HPF) diets are validated options — both reduce pruritus scores and dermatitis severity scores during the EDT and are well-tolerated. 1 Serum food-specific IgG, saliva antibody testing, and intradermal testing are unreliable for diagnosing food allergy in dogs and should not be used to select or exclude proteins. 4 Over half of dogs with CAFR require more than 4 weeks to show a pruritus visual analog scale (PVAS) decrease ≥2 or any decrease in CADESI-4 score, which means early improvement cannot be used to rule out food allergy, and the full trial duration is necessary in most cases. 1 A shortened EDT is achievable when antipruritic therapy is used in the initial phase: prednisolone administered for the first 2–3 weeks controls inflammation sufficiently to allow food challenge earlier than the traditional 8 weeks in dogs that remain relapse-free after prednisolone discontinuation. 35 When using the shortened prednisolone-assisted protocol, the diagnostic threshold of one relapse or fewer after prednisolone discontinuation carries a sensitivity of 95% and a specificity of 100% for food-induced atopic dermatitis. Oclacitinib can substitute for prednisolone in this protocol, but at the same threshold of one relapse or fewer, sensitivity drops to 63% while specificity remains 100%. Initial treatment duration (2 vs. 3 weeks) does not influence the outcome. 5 Dogs that never achieve 2 weeks off medication without relapse should complete the full standard 8-week EDT. 5 The 2023 AAHA guideline specifies the following assessment pathway during the EDT: antipruritic the