Let’s chat about food allergies and elimination diet trials!

What is a food allergy?

A food allergy is the body’s abnormal reaction to a presence of an ingredient. When this happens your pet’s body can react in different ways. To diagnose if your pet has a food allergy, the sole diagnostic tool is to perform an elimination diet trial!

What is an elimination diet/food?

Simply put, it’s any food that we think doesn’t contain the ingredients that your pet may be allergic to. Elimination diets, also called “hypoallergenic” diets, fall into two categories: novel ingredient diets and hydrolyzed diets.

A novel ingredient diet is made from foods that your pet has never eaten. This makes the ingredients new, or “novel”, to their immune system. The immune system usually tolerates these ingredients because there hasn’t been time for an allergy to develop. A novel ingredient diet can be veterinary diet or a home-prepared diet, based on your veterinary team’s recommendation and your preference. Although they can be very effective, there are a couple of drawbacks to novel ingredient diets. It can be difficult to find ingredients that are truly novel if a pet has already “eaten everything on the Ark”. And researchers suspect that in some cases, pets can cross-react to ingredients that they have never eaten. For example, some dogs allergic to beef may show symptoms when fed lamb or venison, even if they have never eaten these meats.

A hydrolyzed diet is made with ingredients that are broken down (hydrolyzed) in a way to make them very small. These tiny fragments are so different from the full-sized protein that they are much less likely to trigger an allergy. So even if your pet has an allergy to soy, they might safely be able to eat a food made from hydrolyzed soy. Hydrolyzed diets can be a good choice in pets that have eaten a wide variety of foods and treats.

An anallergenic diet, such as Royal Canin Anallergenic, is made very similarly to hydrolyzed diets however the ingredients are broken down (hydrolyzed) even further and are paired with a purified starch. Royal Canin manufacturers this specific diet in a separate factory from their others, and they guarantee that this formula and the manufacturing of this formula excludes sources of food allergens. They also complete extensive quality control processes that include DNA analysis to ensure the formula has not become contaminated in any way. For this reason, this diet is often our number one choice when it comes to completing an elimination diet trial as it will provide us definitive answers on whether we may be dealing with a food allergy for your pet.

In addition to being hypoallergenic for your pet, the food must also be one that they digest well and eats happily for 8 weeks. Each pet is different, so sometimes we must try a few different foods before we get it right! It is amazing to think that we now have the technology and knowledge to formulate these amazing diets! These types of diets have had such a positive impact on our pets’ lives. As veterinary professionals we are grateful to have access and the knowledge to use these diets!

Why is my veterinary team recommending a prescription diet/food?

Our therapeutic or prescription diets are recommended over pet store diets for a few reasons:

  • They are scientifically formulated by veterinary nutritionist, veterinarians, and researchers.
  • They have performed extensive research and trials.
  • These diets are produced in factories that only produce one diet or who have the highest set of sanitation standards to eliminate any cross contamination with other diets.
  • They are palatable, our pets still enjoy eating them!
  • There are no hidden ingredients.

There are many great diet options, a few diets that we recommend are made by Royal Canin, Hill’s and Purina. Here are just a few you may have heard of or used yourself!

  • Royal Canin Anallergenic
    • Find dog version here.
    • Find cat version here.
  • Royal Canin Hypoallergenic Hydrolyzed Protein
    • Find dog version here. And small dog here.
    • Find cat version here.
  • Royal Canin Selected Protein – PD or RC (Novel Protein)
    • Find dog version here.
    • Find cat version here.
  • Purina HA Hydrolyzed – Chicken or Vegetarian
  • Hill’s z/d (Hydrolyzed Chicken)
    • Find dog version here.
    • Find cat version here.
  • Hill’s d/d (Novel Protein)

Will I need to feed the recommended diet/food forever?

In most cases, no. Even if your pet has a food allergy, your veterinary team can often recommend foods other than the trial diet that will work for long-term feeding. And of course, if your pet does not improve by 8 weeks, there is no reason to continue the food.

What is an elimination diet trial and how do I complete one?

An elimination diet trial is completed by feeding one specific diet recommended by your veterinary team for a period of at least 8 weeks straight. This is done by eliminating all other foods, treats, human food, etc and feeding your pet only one thing; the new diet. By eliminating all other substances, we hope to see improvement in your pet’s symptoms. If there is no improvement this will also be a great indicator for your veterinary team on how to move forward with diagnosing your pet’s allergies.

Step 1: Order the food your veterinary team has recommended for your pet via the Central Vet online store (shop.centralvet.ca).

Step 2: Before starting your pet’s diet trial, thoroughly wash out the food container and dispensing cup so that there is no residue from the previous diet to interfere with the diet trial.

Step 3: Once your pet’s food order has arrived and has been picked up/delivered*, slowly transition your pet from their old food to their new food by following the chart below.

Step 4: Day 1 of our diet trial starts when your pet is completely transitioned 100% from their old food to their new food (day 7). Continue this trial for 8-12 weeks.

Why is the elimination diet trial so long?

It takes a long time for the skin to normalize after a food allergen is removed. A diet trial lasting 8 weeks will diagnose about 95% of food allergic pets. On the other hand, a trial lasting 4 weeks will diagnose only about 50%.

Some of our tips for elimination trials:

  • Tough love. You will need to be strong when confronted with those big brown eyes asking for a treat. Think of the possible health benefits for your pet. Or imagine a peanut-allergic child asking for a peanut butter cookie!
  • Don’t give up. Though we always recommend a food that we think is best for your pet, what your pet actually thinks matters most. Call your veterinary team if you encounter food refusal, diarrhea, or any other problems. Many prescription diets are guaranteed, so the food can be returned and replaced with another if your dog doesn’t like it.
  • “Good dog!” Make the food into a treat by putting it into your pet’s cookie jar and using it as a reward. If your pet gets food from the kitchen counter or table, have a stash of the food at these locations. You can even hide it in a food-dispensing toy to make it more fun for your pet. Some pets prefer options (which is understandable), and in this case we recommend using liquid smoke! Their diet trial food is placed in a sealed container for 1-3 days with a liquid smoke flavour of your choice. By doing so, we disguise their kibble taste with liquid smoke flavour while also keeping to our strict diet trial.
  • No stealing! Feed your pet separately from other pets to make sure they don’t sneak into their bowls.
  • Don’t mix and match. Stick to one type of food during the trial. For example, don’t add a venison canned food with a hydrolyzed dry food. No one food is 100% hypoallergenic for every pet, so feeding more than one type increases the chance of “missing” a food allergy.
  • Oh no, pills? If you struggle to give oral medications to your pet, ask your veterinarian about alternatives such as injections or topically applied treatments, or even delaying the diet trial.
  • Let your pack know. Your pet may have an entourage: children, neighbours, dog walkers, dog daycare staff, pet store staff, and members of your family. They need to know about the diet trial!
  • Plan ahead. Purchase the food well in advance of when you will run out. You may even choose to set up a subscription via our online store (shop.centralvet.ca) to save you from forgetting to reorder.
  • Keep track. Keeping a calendar of your pet’s symptoms, medications, and food can really help our team figure out what’s working, and what’s not.
  • Don’t panic! If you make a mistake, it’s okay. Record it on the calendar and keep going with the diet trial.
  • Stay strong. For the sake of your pet’s health, do your best to stick with the trial for the whole 8 weeks.

Call or text our veterinary team with any questions, or to ask for help. Yes, feeding only one food to your pet can get challenging but, in the end, we will get results!

*Delivery through our MEDDs delivery service is currently available within Winnipeg and St. Norbert.




Written by Stephanie Guenette, RVT with additional training in veterinary nutrition.
Learn more about Stephanie here.