Food allergies & hypoallergenic diets

Often when pets have diarrhea or a skin condition, people immediately jump to the conclusion that their pet has a food allergy. True food allergies in pets are fairly rare (10% of all allergic pets) but they do happen, and can be diagnosed through something called a food elimination trial. This is a strict diet where every possible allergen is removed from the diet and replaced with a carefully crafted, hydrolysed, complete prescription food, and then the pet is provided with a series of dietary challenges to determine what protein (or more infrequently carb) sources they are unable to tolerate.

Certain breeds are pre-disposed to allergic skin and GI conditions

Food allergies in pets show themselves in many different ways. Pets can show gastrointestinal signs such as vomiting, diarrhea, borborygmus (noisy guts), flatulence, increased frequency of bowel movements, and/or blood and mucus in the stool or they may show dermatological signs such as scratching, alopecia, chewing or licking themselves particularly around the groin or belly, ear infections and scabs and sores around the head, neck and chin. If your pet shows any, or all of these signs, you should seek the help of your veterinarian to move forward with a dietary trial and investigation. To start this off, your vet or nutritionist will select a true hypoallergenic diet to feed for the trial. It is not recommended you commence your own trial at home or switch to a diet labelled ‘hypoallergenic’ without discussing it with your vet, as many foods claim to be hypoallergenic when they are in fact not.

Excessive licking can be a sign of food allergies

Hypoallergenic foods

For a food to be truly hypoallergenic, it must not contain anything that the pet can react to. Majority of food allergies in pets are caused by animal proteins such as chicken, beef, lamb and fish. Some foods that claim to be ‘hypoallergenic’ still contain these products and instead are grain free claiming that grain allergies are the most common form of food intolerance in pets. Although grain allergies can occur, they are incredibly rare making up less than 1% of food allergies in pets, meaning the other 99% is caused by proteins. The other issue is, the allergens included in the food are not hydrolysed – when a protein is broken down through enzymes, it is cut into smaller pieces that cannot be recognized by the body’s immune system to attack it and react. This is an incredibly expensive and involved process. When formulating these foods that are hydrolysed, they are also tested to ensure that they do not contain any foreign DNA particles that the body could recognise as an allergen and are created in dedicated factories that do not manufacture anything other than this food thus preventing the chances of any cross contamination. Small independent companies that do not have dedicated facilities for their ‘hypoallergenic’ foods simply cannot ensure there is no cross-contamination, and do not have the funds to perform the hydrolyzation process and then DNA test afterwards. Other diets that claim to be single or limited ingredient may be suitable after a dietary trial, if your vet has confirmed an allergy is present to a specific allergen, but again you cannot guarantee there is no cross contamination if the product isn’t manufactured in a dedicated facility.

Food allergies in pets make up less than 10% of all allergies in pets

Foods that are safe for dietary trials:

  • Royal Canin Hypoallergenic (also known as Hydrolysed Protein): hydrolysed soy protein, suitable for puppies
  • Royal Canin Anallergenic (also known as Ultimo): extremely hydrolysed feather protein
  • Hills Z/d: hydrolysed chicken protein
  • ProPlan HA: vegetarian version is hydrolysed soy protein

Products you can use after the dietary trial:

  • Royal Canin Sensitivity Control: duck and tapioca, also contains hydrolysed chicken
  • Hills D/d: venison and potato, grain free for pets with true grain allergies
  • ProPlan HA: hydrolysed soy protein and hydrolysed chicken as flavour

All the diets mentioned above are complete and balanced for long term feeding, so if you prefer to stay on the diet after the trial finishes or can’t find a diet that suits your pets allergies, it will not be harmful.

How to perform a food elimination trial

A proper food elimination trial should last for a minimum of 8-12 weeks and should be overseen by a veterinary professional to ensure it is being carried out correctly and to provide medicated relief if your pet has a flare up during the challenge phase of the trial. You can continue with your medications throughout the trial as it will not effect the response we see and will help with the recovery. Many pets’ symptoms resolve by Weeks 6-8, but do not be discouraged if you don’t see much improvement before the 8 week mark.

Week 1: Transition onto the elimination food over a seven day period. This is typically a hydrolysed prescription food (as discussed above) purchased from your vet to reduce the chances of cross contamination.

Weeks 2-4: Feed the elimination food exclusively – nothing else must enter the pet’s mouth. No treats, human food, probiotics or supplements, flavoured toothpaste etc. During this period, you will want to monitor your pets symptoms and keep a diary of the severity. Follow up with your vet or nutritionist at Week 4.

Weeks 4-8: Continue to feed the elimination diet with nothing else. Majority of pets symptoms completely resolve after 6-8 weeks, so you should start to see some significant improvement by now.

Weeks 8-12: Begin challenging. Introduce one protein source at a time, every two weeks – most of the reactions appear within four days. Again, keep your diary to monitor what symptoms occur when a protein is given. I always recommend starting with the protein sources first such as chicken, beef, pork, lamb, turkey, fish and eggs then move onto carbohydrate sources such as soy, corn, wheat, oats, rice. Follow up with your vet at the conclusion of the trial to review your food diary.

At the conclusion of the trial, you should now have a good idea on what allergens are a problem for your pet and this can help guide you on choosing a new diet for your pet. If you didn’t see any change at all throughout the challenge, a food allergy is unlikely and environmental allergies are probably the culprit for your pets discomfort.

What about other tests?

Blood, saliva or hair tests that claim to test for food sensitivities and allergies are a complete waste of money! They are not diagnostic of food allergies and a recent study showed they largely picked “allergies” at random – even diagnosing samples of fake fur and water with allergies to various foods. For this reason, veterinary professionals do not recommend these tests and the gold standard to test for a food allergy is a strict food elimination trial. This allows us to exclude everything from the diet and then one by one, add back in suspected allergens and monitor the pet’s response to them. With majority of allergies in pets being due to environmental allergens (90%), if your pet doesn’t show any improvement or change during a food elimination trial, you won’t need to restrict or change their diet at all, and can instead focus on treating the actual environmental causes. In these cases, a referral to a Veterinary Dermatologist may be helpful. If you want to further investigate environmental allergies, you can have a intradermal allergy or skin prick test conducted by a Veterinary Dermatologist; they can determine which allergens are a problem for your pet and formulate a ‘vaccine’ to improve your pet’s tolerance of these allergens and reduce their allergic response.


Has your pet been through a food elimination trial? Does your pet suffer from food or environmental allergies? Tell us about your experience in the comment section below!

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3 thoughts on “Food allergies & hypoallergenic diets

  1. Pingback: 5 signs you need to change your pet’s diet – nutrition rvn

  2. Hi. I am a dog trainer and many of my clients are on hydrolyzed protein diets….and are never even told about doing the trials. Meaning the dogs spend the rest of their lives with no variety in their diet. It also makes training difficult as for many of the dogs they cannot have treats and are not terribly motivated by the food itself.
    I think not discussing food trials with a client is poor care, to be honest, especially given the very high cost of the food. As with the other prescription diets, I absolutely agree that they are needed when an animal has an issue but should there not be encouragement to actually figure out the sensitivity itself?

    Liked by 1 person

    • I definitely agree Maggi. It’s very important to discuss the elimination trial when starting these diets to determine what the sensitivity is, because it really does open up possibilities for the pet. I always recommend we complete the challenge phase of the elimination trial and choose a diet based on the results. Unfortunately some clients see such good results on the food, they are reluctant to transition off the hydrolysed diet which is why some will stay on it long term. Communication between the client and vet team is very important when starting any new diet.

      Liked by 1 person

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