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My Dog is Allergic to Chicken!
Are food allergies really that common in pets?
Dr. Caitlin Grant, BSc, DVM
Dr. Adronie Verbrugghe, DVM, PhD, Dip ECVCN
Food allergies in cats and dogs are not that common. For healthy dogs and cats, there is no scientific reason to avoid chicken or grains. If your cat or dog has been diagnosed with an allergy, always seek the guidance of your veterinarian when making a decision on what food to feed.
Food allergy, adverse food reaction or food intolerance are terms that pet owners and veterinary professionals will use to describe a situation when an animal appears to have a reaction to a specific food ingredient, but what do those words actually mean and are they all the same? An adverse food reaction is the broad term used to describe a sensitivity to a food and this term can be divided further into two categories: immunological reactions and non-immunological reactions 1. An immunological reaction following food intake is termed a food allergy or food hypersensitivity whereas food intolerance refers to a non-immune mediated reaction 2. Food hypersensitivity can manifest with either cutaneous (skin) lesions or with gastrointestinal (GI) symptoms and can be immediate, intermediate or delayed. A delayed hypersensitivity is non-IgE mediated whereas immediate and intermediate hypersensitivities are both IgE mediated. This is also referred to as anaphylaxis. Food idiosyncrasy, food poisoning, food intoxication, as well as pharmacologic and metabolic reactions to food fall under the food intolerance category 2.
The true prevalence of food allergies in dogs and cats is not known but has been reported with a wide variation 4. A review of several reports has suggested that of the total dogs presenting to a primary care veterinarian with a form of dermatosis, between 1 and 6% are due to a food hypersensitivity. This review also reported that of the total dogs and cats presenting with an allergy, between 10 and 49% are due to food allergies 2. These numbers are higher when looking at dermatology specialty referral practices 4. Animals can also become sensitized to environmental allergens and can show similar skin symptoms as with a food allergy. In a dog or cat with skin lesions as the primary problem, it is important to determine if the underlying cause is an environmental allergy, food allergy, or even both.
When considering what will cause an allergy in a dog or cat, proteins are the most likely culprit, though in theory any molecule in the diet could cause an allergy 4. Is chicken the most common allergen? According to a review that included 15 canine studies, 69% of reported cases identified beef, dairy products and wheat as offending allergens whereas 25% of the cases identified lamb, chicken egg, chicken and soy 2. The same review looked at 10 feline studies and found that 80% of reported cases were associated with either beef, dairy products or fish.
If a food allergy is suspected, a food elimination trial must be conducted in order to confirm the diagnosis. An elimination trial involves selecting a hydrolyzed food or a limited ingredient food (one carbohydrate and one protein source) and feeding this exclusively for several weeks. Improvement in clinical signs should be observed within the first few weeks but it can take up to 4 weeks for gastrointestinal signs and up to 10 weeks for dermatologic signs to resolve 1,4. Once this elimination phase has been completed, the challenge phase must follow. During the challenge phase, foods suspected to cause an adverse reaction are reintroduced. A positive reaction i.e. return of the clinical signs confirms the food allergy. It is important to note that some limited ingredient foods, especially if a homemade diet is chosen, will not be complete and balanced and should therefore not be fed exclusively long term. Once a food allergy has been confirmed, you can work with your veterinarian or a veterinary nutritionist to ensure your dog or cat is receiving a complete and balanced diet for long-term health. Other methods including intradermal skin tests, skin biopsy, saliva testing, and serum testing for allergen specific IgE are not reliable for confirming a food allergy but can be useful for confirming an environmental allergy 3.
If your dog or cat has been diagnosed with a food allergy, always seek the guidance of your veterinarian when making a decision on what food to feed. As noted above, you have two main options to consider. The first option, often considered the golden standard to diagnose and treat food allergy, is to select a hydrolyzed protein diet. Hydrolysis is a process by which the protein molecules are cleaved into smaller segments and by shortening the protein molecule, there is less of a chance for an immune reaction to occur 5. Hydrolyzed diets are veterinary therapeutic foods and thus must be purchased from your veterinarian. These diets have been reported to be effective and well tolerated as elimination diets in most pets, even when sensitized to the intact protein source. However, some animals sensitized to the intact compounds may still react adversely to the hydrolyzed diet. This could be a reaction to the hydrolyzed protein, but also to other proteins present in the diet. The second option is to choose a food with “novel” ingredients. The term novel is used to describe ingredients that are not commonly used in pet food and an individual dog or cat has not been exposed to. This can be very different depending on the pets’ diet history. For example, potato and salmon could be novel for a dog that has only ever had chicken and rice – but would not be novel for a dog that has eaten salmon or potato in the past. Selecting a food with novel ingredients could be challenging if your dog or cat has been fed a variety of foods throughout its life. While there are many over-the-counter foods with novel ingredients, choosing a veterinary therapeutic food, at least initially, is recommended because of increased quality control and decreased risk of cross contamination with the veterinary therapeutic foods. Furthermore, over-the-counter foods may advertise limited ingredients on the front of the bag but have protein and carbohydrate ingredients listed on the back, making it difficult to choose a product with novel or limited ingredients. If a homemade diet was used for the elimination trial and you want to continue feeding this, you can work with a veterinary nutritionist to make sure the recipe is complete and balanced for your pet. In the end, no matter which diet is chosen, it is often a process of trial and error. There is no one diet that fits every dog or cat with a food allergy.
In summary, food allergy is a term that can be misused as there are a number of types of food sensitivities that do not involve the immune response required to be a true allergy. Food allergies in dogs and cats are not that common, however, if you do think your dog or cat is suffering from a food hypersensitivity, you should consult with your veterinarian and talk about whether a food elimination trial could be indicated. For maximum confidence in performing an elimination diet trial, it is crucial, even when using a hydrolyzed protein diet, to provide an accurate dietary history, as this will guide your veterinarian to choose a diet that contains ingredients the patient is unlikely to be sensitized to. It is important to remember that dogs and cats need nutrients, not ingredients, and that these nutrients can come from a variety of ingredients. For animals with true food hypersensitivities, ingredient selection is an important consideration. For healthy dogs and cats, there is no scientific reason to avoid common ingredients like chicken or grains.
1 Verlinden A, Hesta M, Millet S, Janssens GPJ. Food allergy in dogs and cats: A review. Crit Rev Food Sci 2006; 46: 259-273.
2 Roudebush P, Guilford WG, Jackson HA. Adverse reactions to food. In Hand MS, Thatcher CD, Remillard RL, et al. (eds): Small Animal Clinical Nutrition, 5th ed, Topeka, Kan, 2010, Mark Morris Institute.
3 Saridomichelakis MN, Olivry T. An update on the treatment of canine atopic dermatitis. The Veterinary Journal 2016; 207: 29-37.
4 Kwochka KW, Acvd D. Cutaneous adverse reactions to foods food trials and diet options. Kentucky Vet Med Assoc. 2010.
5 Cave NJ. Hydrolyzed protein diets for dogs and cats. Vet Clin Small Anim. 2006; 36:1251-1268.