Pet Food Allergy: Questions, Concerns, and Remediation

Ramesh Khanal, Ph.D., PAS, Dipl (ACAN), June 14, 2020

Many pet owners may be wondering about the food allergies in their pets. More so because of the hype caused by all the marketing and promotional efforts employed by hundreds of pet food companies in selling their brand, a specific product or to differentiate themselves from the competition. 

Is it really that prevalent?

Short answer: not much. More than reality, its actually the perception. It’s often the thought that my pet is unique and special, which they are, and therefore, allergic to this particular food item or that, which most likely they are not. While it occurs in some cases, under 5% as per Dr. Deborah Linder at Clinical Nutrition Service at Tufts University, the reactions about your pets’ itchy skin, loose stool, vomiting, or ear infection is probably the result of some other issues rather than actual food allergy. In reviewing many research findings published in peer reviewed scientific articles sometime back, Wills and Harvey (1994) found it rare for cats and dogs to have food allergies. Similarly, recent studies by Udraite Vovk et al. (2019) and Lam et al. (2019) also indicate that food allergies in dogs and cats is not common. Overall, even that 5% is likely an overestimation. Such allergies are likely more prevalent among neglected and rescue pets.

What is actually food allergy?

Food allergy (or cutaneous adverse food reaction) is basically a triggering of the immune response to any given food after its ingestion by the animal, pets in this case. Such an immune response causes cells in the body to release histamines or compounds that lead to itching and many other allergic signs. Usually, it occurs when a particular food is fed over a relatively long period of time. Often, it may be a couple years, not weeks or months, to actually see the food allergies occurring in pets. Most often, it is related to the animal protein component of the food, be it the beef, chicken, poultry, fish etc. Among plants, wheat or soy are more likely to trigger the effect. At the structural level, food allergens are (glyco-)proteins with a molecular weight from 10–70 kDa that are resistant to treatment with heat, acid, and proteases (enzymes that help digest proteins). 

Food allergy test in pets:

Scientific determination of actual food allergy in pets is rather complex and involves food elimination and re-introduction, one food at a time. Clinical signs are rather variable, pruritus (or itching) being considered the major one. So, in theory, higher the number of ingredients in a given food the more complex it gets to do the testing. Since animal proteins are some of the major culprits, one needs to look at that first.  

There is no easy diagnostic test available and those claiming to have done some blood testing for food allergy is basically fooling the customer to sell their mediocre product or appear different from the competition. Dr. Carolyn Heinze at Clinical Nutrition Service, Tufts University states that “Saliva and blood tests for food allergies in dogs do not reliably distinguish between healthy and allergic dogs and should not be used for diagnosis of food allergy!”. Pretty much the same applies to cats. Two scientific studies published recently in peer reviewed journals (Udraite Vovk et al., 2019; Lam et al., 2019) clearly prove the point. So far, diet elimination study is basically the only viable test for food allergies in pets, but that may not be as feasible under commercial or mass scale testing. 

The most reliable is the food elimination test. Here, whatever the current food is provided to the pet is removed completely. In its place is given a very specific diet, mostly either with a hydrolyzed protein source or some specific novel protein sources to which the pet hasn’t been exposed to before. The diet is fed for some time and monitored for any immune response. If the immune response is triggered, then some other protein source is used and the process is repeated again until the culprit is identified. Once the allergen is identified, then the recipe without that particular food component is most likely created for long term use. Given the more individualistic nature, this approach may or may not be as appropriate for everyone.  

Allergy vs intolerance:

Food allergy (FA) is defined as “all immune-mediated reactions following food intake,” in contrast with food intolerance (FI), which is non-immune-mediated. Another critical difference between the two is that intolerance can occur with even a single exposure, whereas allergy requires rather long term exposure. A very common example that can be applied to both humans and pets is the lactose intolerance, which happens when a dog's body just doesn't process lactose found in milk and milk products very well, leading to gastrointestinal disorders, diarrhea being the most common one. However, signs of dog food intolerance can often look pretty similar to the signs of a food allergy, both of which can manifest in itchy skins.

Primary foods responsible for allergies:

As stated previously, its actually the animal protein associated with food allergies if and when it occurs. Unlike in humans, plant proteins, such as wheat glutens, are linked to much fewer food allergies in pets, 13% with wheat glutens vs 34, 17, and 15% for beef, dairy products, and chicken, respectively (Mueller et al., 2016). Below are some of the most common allergens in pet foods as per Mueller et al. In the case of cats, fish appears to be right after chicken.

Remediation:

Since it takes quite long to develop allergy to any given food, food ingredients to be more specific, it may be wise to change the protein sources regularly or may be rotate between several sources, such as poultry, beef, pork, turkey, fish, etc. That’s probably the reason why there is an overabundance of testimonials claiming the food allergies being cured by switching to a different brand. Most likely, it may have been the protein source that was changed and therefore, the pet hasn’t been exposed to that food long enough to trigger the immune response.

While switching just the protein source can be a good short term option, rotation of protein sources would most likely provide better preventive results given it takes a rather long exposure to potential allergens to trigger the immune response. Sometimes, it may be late in their life that pets become food allergic after getting exposed to the same diet for so many years. Further, switching the entire diet before they are exposed for long enough of a duration should also help quite well and prevent your friend from food allergy. One need to be cautious though when switching the entire diet by offering it gradually over a period of 7-10 days or slightly longer. Finally, another option would probably be to go through diet elimination process to identify what food component(s) exactly caused the allergy in the first place. However, this is a rather long and expensive process involving many a trip to their vet and a majority of pet owners may simply want to avoid that. One can simply try other options before getting to this last resort.  

Below are links to several articles, mostly scientific and peer reviewed but also some not so scientific, for pet owners to actually understand and determine whether food allergy issue in pets is hyped up to sell a given product or you need to be really concerned with your own pet about that. Some would also provide further guidance as to how you may be able to take care of it on your own. 

Udraite Vovk L, Watson A, Dodds WJ, et al. Testing for food-specific antibodies in saliva and blood of food allergic and healthy dogs. Vet J 2019; 245:1-6.

Lam ATH, Johnson LN, Heinze CR. Assessment of the clinical accuracy of serum and saliva assays for identification of adverse food reaction in dogs without clinical signs of disease. JAVMA 2019; 255:812-816.

Clinical Nutrition Team, Tufts University: What every pet owner should know about food allergies, https://vetnutrition.tufts.edu/2017/01/food-allergies/

Verlinden et al (2006). Food Allergy in Dogs and Cats: A Review.  Critical Reviews in Food Science and Nutrition, 46(3), https://www.tandfonline.com/doi/abs/10.1080/10408390591001117 

Wills and Harvey (1994). Diagnosis and management of food allergy and intolerance in dogs and cats, Aus. Vet. J.,  https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1751-0813.1994.tb00907.x 

Mueller et al (2016): Critically appraised topic on adverse food reactions of companion animals (2): common food allergen sources in dogs and cats. BMC Vet. Res. 12 (9). DOI 10.1186/s12917-016-0633-8   https://bmcvetres.biomedcentral.com/track/pdf/10.1186/s12917-016-0633-8

Cornell University’s Feline Health Center: Food Allergies, https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/food-allergies

Clinical Nutrition Team, Tufts University: Research Update: Testing for Food Allergies, https://vetnutrition.tufts.edu/2020/03/food-allergy-testing/

Anna Burke - Dog Allergies: Symptoms and Treatment, https://www.akc.org/expert-advice/health/dog-allergies-symptoms-treatment/

E. Linder (2019). Can I change my pet’s diet to improve skin and coat health? https://vetnutrition.tufts.edu/2019/09/can-i-change-my-pets-diet-to-improve-skin-and-coat-health/