Myths and Truths: Food Allergies in Dogs and Cats
Written by Christine Zewe, DVM, DACVD
Food allergies in dogs can cats can cause several issues, including gastrointestinal upset and skin and ear issues. Pets with food allergies can have the same symptoms as pets with environmental allergies and other GI problems, making the overall picture even more complicated to diagnose.
In this article, we will debunk several of the common myths associated with food allergies in dogs and cats, and hopefully provide you with a better understanding of this complicated topic.
Myth #1: Food allergies are the most common cause of allergies in dogs and cats.
Truth: In regard to the skin and ears, food allergies only account for a small percentage of allergic dogs and cats. An analysis of all published studies about food allergies and dermatitis showed that food allergies occur in up to 24% of dogs with skin diseases and up to 21% of cats with skin disease. The estimate may be slightly higher in dogs with other types of allergies, such as environmental allergies. Overall, food allergies affect between 1-2% of all dogs and cats. So, while these numbers are certainly significant enough to warrant evaluation for food allergy in many patients, they also show that more often than not, something else is plaguing your pet.
Myth #2: Pets are usually allergic to grains.
Truth: Most pets with food allergies are allergic to the protein in the diet, not the carbohydrate source. The most commonly reported allergens in dogs are beef, dairy products, chicken, wheat, and lamb. In cats, the list includes beef, fish, chicken, and wheat. In order for a pet to develop an allergy to a food, they have to be exposed to it repeatedly. The most common allergens in pets are often the most common proteins in foods, treats, flavored medications, and chew toys.
Myth #3: Blood, skin, hair, and saliva testing can tell you which food your pet is allergic to.
Truth: These tests are considered to be unreliable, at best, for testing for food allergens, and most dermatologists do not recommend performing them. Studies have shown that for food allergens, there is no commercial test available today that meets all of the basic standards for good diagnostic tests. The “gold standard” test for a food allergy remains an elimination diet trial, in which the pet is fed a diet made from a protein they have never eaten or a hydrolyzed protein (hydrolyzation breaks down large proteins into smaller pieces, making them unrecognizable to the immune system), and then a “re-challenge” at the end of the trial period. Patch testing, a very specialized type of allergy test, may be performed to help select the correct protein source for the diet trial, but cannot be used in place of a diet trial for a diagnosis and is very rarely performed in practice.
Note: while no good test exists for food allergens in pets, blood and skin tests are reliable for identifying environmental allergens.
Myth #4: My pet can’t have a food allergy, they have eaten the same thing their entire life!
Truth: Dogs and cats can spontaneously develop and allergy at any stage in life, including puppyhood or mature adulthood. Even a 10-year-old dog with no history of allergies can suddenly develop a food allergy, seemingly out of nowhere!
Myth #5: Chicken is bad!
Truth: Chicken is only bad if your pet is allergic to it. There is nothing specifically allergenic about chicken that makes it more likely than any other protein to cause a food allergy, it is just a common protein source that most pets have been exposed to! If you are concerned that your pet may have a food allergy, work with your veterinarian to select a food appropriate for an elimination diet.
Myth #6: My pet can’t have a food allergy, we changed the diet a month ago and they are still itchy!
Truth: Diet trials in pets should last a minimum of 8 weeks, which is long enough to diagnose 90% of food allergies, and can be extended up to 12 weeks. The changes in the skin and ears will likely be slow, and it may be 5 or 6 weeks before you notice any major changes at home. Strict adherence to the new diet and patience are important keys for performing a successful diet trial.
About Christine Zewe, DVM, DACVD
Originally from Texas, Dr. Zewe received her Bachelor’s degree in Finance from the University of Texas at Austin. She then attended Louisiana State University, where she earned her Doctorate in Veterinary Medicine and completed a rotating internship in Companion Animal Medicine in Surgery. Dr. Zewe completed her residency in Dermatology at Tufts University in 2017. Dr. Zewe was accepted as a Diplomate in the American College of Veterinary Dermatology in 2017.
Dr. Zewe enjoys managing various kinds of skin disease, but take a special interest in managing otitis and allergic skin disease.