Think Your Pet Has a Food Allergy? Here's What You Should Know First

If a pet is itchy or is having gastrointestinal problems, one of the first things pet parents tend to blame is their food. It is common for pet parents (and even, sometimes, veterinarians) to point to the food when their dog or cat is itching for no apparent reason. However, there is limited data regarding the true incidence of food allergies and intolerances in dogs and cats. One published meta-analysis based on several other studies indicated that cutaneous adverse food reactions (CAFR) observed in veterinary clinics affected between 1% and 2% of all dogs in the evaluated data. For all cats presented to veterinarians in the studies, that number dropped to less than 0.2%. The authors stated, however, that the limitations of this analysis could include geographic differences as well as the criteria used to diagnose CAFR. CAFR is a medical term that describes the symptoms associated with a food allergy.  

The key takeaway is that food allergies and intolerances are not very common in our pets, and other causes of itchiness in dogs and cats should always be ruled out first. 

The most common types of allergies that manifest as skin problems in pets are flea bite allergies. Even though pet parents may not see fleas on their pets, for some highly allergic individuals, even one flea bite can trigger an immune reaction leading to itchy skin. Other types of allergies that we see in our pets include environmental and contact allergies. Environmental allergies can be caused by some of the same triggers that humans are allergic to, such as mold, pollen, and dust mites. One of the biggest differences between flea and environmental allergies in pets is that they can vary throughout the year. Of course, in some areas, fleas can survive year-round, and indoor allergens can be present at all times, making differentiation harder.  

It’s always important to rule out flea allergies first. Skin allergy testing can be performed by veterinarians to effectively diagnose environmental allergies. Allergy testing for environmental allergies that relies on blood samples is also available, but is much less reliable. It is important to always rule out flea and environmental allergies before pursuing a food allergy diagnosis in pets. 

Once a pet parent and their veterinarian have eliminated flea and environmental allergies, food allergies can then be considered. However, before delving into that topic, it's important to distinguish between food allergies and intolerances.  

 

Understanding the Differences: Food Allergies and Intolerances 

Food allergies and intolerances can exhibit similar symptoms in our pets, but the main difference is that a true food allergy involves the pet’s immune system, leading to a complex response of inflammatory mediators that can trigger itchy skin or gastrointestinal (GI) problems such as diarrhea, gas, and even vomiting. Food intolerances do not directly involve the pet’s immune system; instead, they arise when a pet has difficulty digesting certain foods, leading to similar GI symptoms as true food allergies. True food allergies typically develop from repeated exposure to the offending food or ingredient. Conversely, food intolerance reactions can occur immediately after a pet eats a problematic food. Once the offending food is identified, managing food intolerances may be more straightforward, as it can simply be avoided in the pet’s diet. 

Food allergies are most commonly caused by an immune-mediated hypersensitivity to certain proteins found in a pet’s diet. Due to various complex immune system pathways, the pet’s body recognizes a protein as an allergen (a substance causing an allergic reaction), triggering the immune system and ultimately leading to symptoms commonly seen with these conditions, such as itchy skin, feet, ears, and GI symptoms. To complicate things, some pets may be allergic to more than one food or protein ingredient. 

 Diagnosing Food Allergies in Pets 

The only way to truly diagnose a food allergy is through an elimination diet test aimed at identifying which food(s) may be causing the problem. This is often easier said than done.  Elimination diets require a commitment from the pet parent to thoroughly understand their pet’s diet history and communicate it with their veterinarian, in addition to adhering to specific diets (sometimes homemade) for extended periods. The elimination diet process should begin with feeding a single protein source that the pet has not eaten and ideally a single carbohydrate source for a specified period of time. This period can be referred to as the “wash out” period, where the pet’s symptoms hopefully will resolve or lessen enough to observe a symptom flare-up upon introducing a new food.    

There is no definitive consensus among veterinary experts on how long this period should be. One retrospective study indicated that over 80% of pets experienced remission of their allergy symptoms within five weeks for dogs and six weeks for cats. When this period was extended to eight weeks, more than 90% of pets showed no allergy symptoms. However, a longer “wash out” period may make it more difficult for a pet parent to feed their pets novel (new) food, especially if it is a home-cooked diet. We recommend working with your veterinarian to determine the duration they recommend for this.   

Once this period of time is complete, one at a time, common food ingredients (usually proteins) are introduced along with the “wash out” diet to see if the pet‘s immune system reacts.  If there is no reaction or previous allergy symptoms noted, it is assumed that the pet is not allergic to that ingredient. Ingredients are systematically introduced to identify what the pet is allergic to. Some of the most common allergens in pets are beef, dairy, chicken, and wheat. 

Once all offending food ingredients are identified, avoiding them in the pet’s diet is critical to prevent allergy symptoms. This can be achieved by feeding novel ingredient diets that do not contain any ingredients identified as causing food allergy reactions.   

One issue that may arise is cross-contamination at either the ingredient supplier and manufacturer levels. We recommend that pet parents contact companies to learn about the steps they take to mitigate cross-contamination.  

Another way to manage pets with food allergies is to feed them hydrolyzed protein diets. These pet foods contain proteins that have been broken down into smaller pieces, called peptides. This process works because when the protein is reduced to small enough fragments called peptides the pet’s immune system does not recognize it as the protein to which it is allergic. In a way, we are tricking the pet’s immune system. Hydrolyzed diets are effective for many pets with food allergies, though some pets may still experience issues. This could be due to cross-contamination, as noted earlier with novel diets, or it could simply be that the hydrolyzed protein was not broken down into a small enough peptide so that the allergic pet’s immune system still recognized it. 

Food for Thought 

All said, food allergies and intolerances are not very common overall. Other causes of the pet’s symptoms should always be ruled out first. When they do occur, food allergies can be difficult to diagnose, but with patience, dedication, and good veterinary guidance, they can usually be managed to mitigate the uncomfortable symptoms associated with them in our pets. 

BSM Partners has experts in product formulation, nutrition, and quality control to assist brands in creating truly novel or hydrolyzed protein diets that help pet parents manage these conditions for their furry friends.  

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About the Author

Dr. Bradley Quest, DVM, is the Principal Veterinarian at BSM Partners. He has practiced clinical veterinary medicine, developed and tested hundreds of pet food and health products, performs extensive animal health research, and helps navigate pet food ingredient approval for clients.