Diet Elimination Trials: How-To

Has your pet received a recommendation for a diet elimination trial for a suspected food allergy (symptoms ranging from GI issues to skin issues)? Read below to learn more about how to successfully complete a trial to ensure the test is truly diagnostic for your pet: (You can also download a printable handout here)

To start a diet elimination trial you must first select an appropriate prescription diet. We do not recommend OTC allergy diets as they often contain ingredients not listed on the label and/or they have been exposed to cross-contamination. In the same vein, we do not recommend selected protein diets as we may not know the patient’s full exposure history to previous allergens. Food allergy/ intolerance trials for skin/dermatology symptoms last 8 to 12 weeks and for GI symptoms 1 to 4 weeks, depending on progress/improvement.

We recommend the following diets (keep in mind that one brand may work better than another and it is dependent on your pet’s reaction which we cannot know ahead of time without the diet trial):


Royal Canin HP also comes in formulas indicated for comorbidities like urinary and renal issues, as well as a weight loss formulation.

It is only available in dry.

The carbohydrate source in this diet is different from the other brands, so if other trials were unsuccessful this brand may be a better fit for your pet. All hydrolyzed protein diets can be used as GI health diets as well.


Purina Pro Plan HA comes in both wet and dry formulations for both cats and dogs. Dog owners can also choose formulations with special flavoring in either salmon or chicken. HA Salmon is labeled for growth in puppies.

They do not have specific formulations that treat comorbidities, but the cat formulation is rated safe for cats with a history of urinary crystals.

When choosing your diet and formulation make sure you feed only dry OR wet during the initial trial as the different versions can have different proteins and carbohydrates present that may affect the trial results.


Hill’s Science Diet z/d is the final prescription diet we recommend for food elimination trials. It is available for both dogs and cats in wet and dry formulations.

In our experiences with the brand, the dry diet is highly palatable but the wet is not due to the consistency of the loaf.

All three diet brands are appropriate for food elimination trials for both chronic GI symptoms and chronic skin issues if it is truly diet/ingredient related.

Additional tips and tricks for a successful and truly diagnostic food elimination trial:

-Store the diet in its original bag only, clean all food and water bowls daily (especially before transition to the new diet), get new food scoops for the bag,  feed all pets in the household the same diet if possible- all of this is to avoid cross contamination and accidental exposure to the ingredients your pet may be sensitive to.

-Make sure your pet that is undergoing the trial does not get any table scraps or treats, cannot access anything outdoors, does not eat things out of the trash, etc. For the first portion of the trial it is extremely important they do not get anything but the diet. Even the smallest amount of their triggering allergen can skew the results of the trial.

-Food elimination trials are the best diagnostic tool to truly diagnose food allergies that are exclusively performed at home with the pet’s family. It is extremely important that all family members are committed to the trial for it to be truly diagnostic.

-Eventually, at the end of the trial time if the pet’s symptoms have resolved we will challenge the diet (if desired by the owner) with the original diet to see if symptoms reoccur. If they do, then you have confirmation that they have a food allergy. Return to the hydrolyzed diet again until your pet is 100% back to normal, then we can slowly add things one ingredient at a time and monitor for symptoms to determine exactly what your pet is sensitive to. We will discuss this process more in depth once the first part of the trial is complete.

-Follow the feeding guide on the bag closely.

-A food elimination trial is far more affordable than the current IGE/ blood testing that is available and it is much more accurate. Don’t waste your money on allergy blood testing when food allergies are suspected.

Remember, you, the pet owner, are the key to success in a food elimination trial. If you need help or advice throughout the journey please do not hesitate to reach out to your veterinary care team at Lifetime. We are here to help you all along the way!

Download the printable handout!

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