Is your pet having ongoing skin or gastro intestinal issues with unknown causes? Have you exhausted all the other causes such as infection, parasites, or anatomy issues? Is your pet’s Veterinarian now recommending a food trial? If so, below is the lowdown on food allergies, what exactly a food trial is, how to properly execute a food trial, and what food options there are.
What is a food allergy?
A food allergy is an immune system reaction that occurs after eating a certain food. Ingredients in pet food may be combined or changed into substances recognized by the immune system as foreign invaders to be attacked. The target of this attack include the gastrointestinal (GI) tract or other organ systems, but in dogs and cats it is the skin that most often suffers the most. The classical signs of food allergies in pets can be itchy lesions on the face, limbs, anal area, and ears. Some other symptoms are ongoing diarrhea and/or vomiting. Symptoms start when the pet is less than 6 months old or starts when the pet is older then 5-6 years old. Food allergies can develop even if a pet has been eating the same food for years with no issues. It takes time for them to develop the allergy. Symptoms do not happen seasonally like with airborne allergens, they are always present. It is also noted that corticosteroids do not help with most food allergy issues.
The pet food companies have done a great job of advertising “grain free” diets, but unfortunately the pet usually is having a reaction to both the protein and/or carbohydrate in the diet. Grains are not bad for our pets. There is no simple test to see exactly what is causing the reaction. To solve the problem the culprit must be removed from the pet’s world. This is why we do food trials.
What is a food trial?
Before beginning a food trial we want to make sure all other possible culprits have been ruled out (parasites, infections, anatomy issues). If there is any secondary skin infection from the lesions, they must be cleared before starting the trial.
A food trial is when a hypoallergenic diet is fed for a period of time deemed by your Veterinarian. If the symptoms resolve, you then switch the pet back to its original food for 2 weeks to see if the symptoms return. If we see relapse, it is recommended to return to the food trial diet and staying on the food indefinitely.
There are no other ways to diagnose a food allergy. Blood tests are not helpful. Blood tests can detect antibodies against certain food proteins but this does not mean that the pet has an allergy. It could just mean the pet has eaten that type of protein before.
What is involved in a food trial?
Food trials are VERY strict in order to see accurate results and everyone in the household must be on board with the instructions. This means the pet shouldn’t have any other protein sources besides the test protein. This includes rawhides, flavored chew toys, flavored chewable medications including heartworm/flea preventions, flavored vitamins, and all treats. Chewable medications will need to be switched to non flavored tablets/capsules and chewable heartworm/flea preventions may need to be switched to a topical brand.
As stated above, the pet is put on a hypoallergenic diet for at least 3 months. No other food/treats can be fed. If symptoms resolve then the pet is put back on their original diet for 2 weeks. If symptoms resume then we can diagnose a food allergy. The pet can then return to the hypoallergenic diet indefinitely. Some owners opt to not go back to the original diet because they do not want their pet to go through the horrible symptoms again. They will just continue the food trial diet indefinitely.
A food trial is very easy in that all you have to do is feed the hypoallergenic diet, but owners tend to find it hard to not feed other treats. Owners will state that the food trial failed, but in reality they were not being as strict as needed.
What are current food trial options?
There are three different types of diets that can be used in a food trial: a novel protein, hydrolyzed protein, or a home cooked diet.
Novel proteins are most commonly used in food trials. They are diets that contain a single protein source and single carbohydrate source. The most important part of choosing a novel protein, is that it has to be one that the pet has never come in contact with before. For example if you choose a venison and sweet potato diet, the pet must not have eaten either one of these protein/carbohydrates in any other food (treats, dry food, canned, etc). It takes years for a pet to become allergic to a food source, so the pet should not be allergic to something new. Pet food companies are starting to make a huge variety of flavors of food/treats, so it can be very hard to find a diet for the pet if the owner tends to feed a variety of different flavored food/treats.
Examples of novel protein diets include venison and potato, fish and potato, egg and rice, duck and pea, and even kangaroo. Several of these diets have been released to the public markets, so it is very important to choose ingredients for the trial that is not found in the pet’s regular diet. Public markets tend to sell these novel protein food for a lot less then Veterinary prescription diets, but they cannot guarantee that there are no additional proteins mixed in. Contamination easily happens because the machines are not thoroughly cleaned with each new batch of food made. Veterinary prescription diets can guarantee that the product does not contain any contaminants. The the machines are thoroughly cleaned/disinfected between batches of food. Most Veterinary prescribed diets have a 100 percent guarantee. This means that if the pet does not like the food, it can be returned for a refund.
Hydrolyzed proteins are diets that contain the smallest amount of molecules of a protein so that the body cannot detect them. Basically, the immune system is tricked into no longer recognizing the protein so it does not trigger a reaction. The downside of hydrolyzed protein diets is that it is not as palatable as it would be with the protein in its original form. Examples of hydrolyzed protein diets include Hill’s Prescription Diet z/d, Purina HA HypoAllergenic Canine Formula, Royal Canin Veterinary Diet Canine Hypoallergenic. These diets also have a 100 percent guarantee. If the pet does not like the food, then it can be returned for a refund.
Home cooked diets are rarely used in food trial diets. It can be very inconvenient for the owner to have to cook the pets every meal and important vitamins/minerals are easily left out of the diet. If an owner wants to pursue a home cooked diet a nutritionist should be involved so that they can make a balanced diet for the pet. Recipes for appropriate diets can be purchased through BalanceIt, rpetdiets.com, or by any nutritionist listed at the American College of Veterinary Nutrition web site.
So how do you find out exactly what protein/carbohydrate the pet is allergic to?
The process to find out what exact protein/carbohydrate a pet is allergic to is not a simple task but it can be done. It can be a very lengthy process. To do this, you add a single/pure protein source (such as cooked chicken, tofu, wheat flour or any other single food) to the test diet with each meal. If the pet begins to show allergic symptoms within two weeks, then that protein source causes an allergic reaction. You must return to the test diet until the allergic symptoms stops and then you can try another pure protein source. If no symptoms show after two weeks of feeding a test protein, then the pet is not allergic to that protein.
What if a diet is unsuccessful?
To determine if a diet was truly unsuccessful we need to make sure the owner was 100 percent compliant (meaning they only fed the test food), parasites are under control, infections are under control, and that the food trial was done for long enough time. If all those boxes are checked, then it is strongly suggestive that an inhalant allergy is the culprit. If this is the case, biopsies by dermatologist is recommended.
By: Jamie McAfee
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“Allergy – Food Allergy in Dogs.” vca_corporate, vcahospitals.com/know-your-pet/allergy-food-allergy-in-dogs
Clinical Nutrition Team. “What Every Pet Owner Should Know about Food Allergies.” Clinical Nutrition Service at Cummings School, 30 Jan. 2017, vetnutrition.tufts.edu/2017/01/food-allergies