Food allergies in pets can manifest in many ways ranging from ear infections and itchy skin to gastrointestinal signs including soft stool, decreased appetite, and belching.
While any dog or cat can be allergic to any food (I even knew a dog allergic to carrots!), the most common allergens in dogs and cats in the USA are beef, chicken, and fish.
Pets can be allergic to grain sources such as wheat and corn but are more often allergic to protein sources (i.e. meats). Most pets with food allergies are allergic to more than 2 individual ingredients - in fact, the average number of food allergens in food allergic pets is 2.4. Pets have often been fed the food they are allergic to for 2 years or more before developing the allergy.
So You Think Your Pet May Have Food Allergies - How Do We Diagnose It?
Diagnosing and identifying food allergies can be a long & arduous process with lots of hard work, but it can also be very rewarding! Once we figure out what your pet is allergic to, we just stop feeding those specific ingredients and your pet will experience relief from his or her symptoms.
Saliva, blood, and skin testing are completely unreliable in testing for food allergies.
Veterinary dermatologists have longed for a quick and easy test for food allergies, but when saliva/blood/skin tests have been put to the test - ie, feeding a patient what they are "allergic to" based on testing, they have failed.
A patient who has a negative test result for chicken allergy, for example, will have a horrible flare of soft stool and itching when fed chicken. The opposite is also true of these tests. Therefore, it is NOT recommended to use these tests for food allergies.
The only way to diagnose a food allergy in your pet is to use a prescription novel (novel meaning different from anything seen or known) or hydrolyzed protein diet. Novel protein diets are a diet using an exotic protein source that your pet's body has never seen before. With food allergies, if your pet has never eaten it, there is no way he or she can be allergic to it because it takes repeated exposure for food allergies to develop.
Hydrolyzed protein diets contain protein that has been chemically broken down into really small pieces so your pet's immune system can not recognize it as protein. Don't worry! Your pet's digestive system will still recognize these foods as building blocks to proteins and will be getting a full and balanced diet.
Your pet needs to eat the novel or hydrolyzed protein diet for 3-4 weeks for GI issues and 8-12 weeks for skin and ear issues to resolve or see improvement. You must be very strict during the diet trial phase and eliminate all other treats, flavored medications, and human foods. At the end of the diet trial period, we perform a "re-challenge" where we feed your pet all his or her old food & treats back - and if your pet has a flare, BAM! We have diagnosed a food allergy!