Food Challenge to Diagnose Cutaneous Adverse Reaction in Dogs

In the literature

Shimakura H, Kawano K. Results of food challenge in dogs with cutaneous adverse reactions. Vet Dermatol. 2021;32(3):293-e80.

The Research …

Elimination diet trial and food challenge testing are the gold standard for diagnosing cutaneous adverse food reaction (CAFR), but many pet owners are reluctant to perform the 8-week food challenge.

This study included 46 dogs with CAFRs and characterized owner-observed adverse reactions to food challenge after elimination diet trial. A 4-week trial using a single-source protein (ie, horse meat, salmon) diet resulted in significant clinical improvement in pruritus scores. All dogs exhibited pruritus during food challenge: 23.9% within 3 to 6 hours and 60.9% within 12 hours. Only one dog developed clinical signs as late as 10 days after food challenge. Dogs were given prednisolone (1 mg/kg every 12 hours for 5 days) when pruritus was observed and returned to the elimination diet.

The most common sites of pruritus after food challenge were the limbs (56.5%) and face (26.1%). Time to recurrence of clinical signs may have been influenced by transit time in the GI tract. Orally administered antigens require a mean time of 3 hours to reach the blood.¹ No other clinical signs associated with CAFR were observed, and none of the dogs exhibited severe clinical signs (eg, anaphylaxis, respiratory signs) after food challenge.

… The Takeaways

Key pearls to put into practice:

• All dogs in the study showed significant clinical improvement after 4 weeks of an elimination diet, but the small sample size may not be representative of the general population. Performing a diet trial for ≥8 weeks is recommended.

• Dogs were given prednisolone (1 mg/kg every 12 hours) when clinical signs appeared after food challenge; a favorable response was observed. Many dogs with CAFR do not respond to a lower dose of prednisolone (1 mg/kg every 24 hours), possibly due to type III or type IV hypersensitivity. Twice-daily administration should be considered.

• Clinical signs other than pruritus are not likely to occur with food challenges. Owners may be more likely to perform food challenge if they understand the risk is minimal and prednisolone is administered once pruritus is observed.