Diet trials for canine allergic reactions

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“The diet trial [is currently] the only way to fully diagnose a dog as a food-allergic dog,” said Julia E. Miller, DVM, DACVD. On a recent episode of VetXChange, Miller joined Adam Christman, DVM, MBA, to discuss diet trials as a treatment plan for canines experiencing allergic reactions.

Food elimination trial criteria

When a patient comes into the clinic because it is experiencing itchiness, clinicians usually consider 3 types of allergies: flea, food, and environment. Once ectoparasites are ruled out as the cause, the clinician should ask the client follow-up questions to determine whether the allergen is environmental or related to food.

Allergies caused by environment typically affect dogs aged 1 to 4 years, though certain breeds, like French bulldog, American bully, and doodle, can experience effects at just 6 months of age.

“If I’m getting a dog that’s itchy before 6 months of age, [I’m implementing a] diet trial,” said Miller. “That’s the first thing on my list every single time.” Similarly, if a dog has never had allergic reactions but becomes itchy at an older age, environmental allergens are an unlikely cause.

Diet trial options

“Once you’ve decided that your patient is the right patient for a diet trial, then you have to decide if your client [is] the right client for a diet trial,” said Miller. She stressed that communication between the clinician and the pet parent is crucial in ensuring the trial’s success. If the client has any stipulations about strictly adhering to their pet’s food plan, then a diet trial may not be the best option. If the client can commit to a few weeks, however, then the next step is choosing a trial that is compatible with that pet and pet parent’s lifestyles.

Highly digestible, low-residue gastrointestinal diets, fiber-enriched diets, elimination diets, and low-fat diets are a few of the trials available and can be broken down into 2 primary diet types: hydrolyzed diets and novel protein diets. Clinicians should determine the patient’s diet history before deciding which trial to try first. “If that dog has eaten a ton of chicken-based products, I am less likely to reach for hydrolyzed chicken-based food,” said Miller.

No matter which diet is tested, it should be prescription. Over-the-counter (OTC) diets can be cross-contaminated with chicken, beef, and pork, which are common allergens and can complicate the diagnosis. Although they are not suitable as a diagnostic tool, OTC diets can later be used for allergy maintenance.

Measuring success in the trial

Miller also noted that communication between the client and clinician does not end after the diet plan is implemented. The clinician may have to check in with the client to ensure the dog is not consuming food outside the diet plan.

“That kibble should be the only thing that goes in that dog’s mouth,” said Miller. Flavored toys, chews, capsules, dental treats, and food from the table can affect trial success. After ensuring the trial has been started, clinicians should check in after 4 to 6 weeks. If there is no change in the patient after the trial is complete, it can be determined that the patient is not allergic to that food, or the patient is not a food-allergic dog.