Perhaps more than ever before, pet owners are increasingly concerned with their animal friend's diet. As pet parents, we take great care in researching ingredients, choosing trusted brands, and sparing no expense to offer the best to our dog or cat. However, there are circumstances under which even the most expensive food cannot protect our friend from illness. Such is the case for food-allergic dogs.
Food allergy is defined as an immune system reaction associated with eating certain foods. The reaction we see in dogs can either present as affecting the skin or the gastrointestinal tract. Symptoms of skin disease as a result of food allergy can mimic that of other causes of allergic skin disease but can include itching, particularly the ears, feet, and undercarriage. Your dog may experience bacterial or yeast infections of the skin. Ear infections are quite common, and may be the only sign of food allergy in some dogs.
Gastrointestinal symptoms that are caused by food allergy might include diarrhea, frequent bowel movements, flatulence, salivating, and less often, nausea. Again, these symptoms can be caused by a variety of illnesses, so narrowing down that list to a food allergy may take time and diagnostic testing. Your veterinarian will want to rule out immediate concerns first, so that treatment can be initiated quickly for more threatening diseases, if found.
Two important distinctions between food allergy and other forms of allergy are seasonality and age of onset. Because dogs are in contact with their food every day, food allergy symptoms do not typically come and go with the seasons. Seasonal allergy for most dogs is worse in spring or summer, then is relieved in winter months. Food allergy, however, will be present year-round.
The age symptoms begin in dogs most often occurs prior to 6 months old or greater than 6 years old. It is difficult for some pet owners to understand why their 8-year-old dog suddenly developed a food allergy, but the truth is the allergy did not suddenly develop. Rather, it has been developing over the course of years, and the physical symptoms of the reaction are now apparent.
Accurately diagnosing food allergy can be challenging. Laboratory testing of blood, hair, saliva, or feces has not proven to be diagnostic with methods currently available. According to the Animal Dermatology Group, "there is no reliable blood test or skin test for food allergy." The diagnosis, then, can only come from, "a properly performed elimination diet trial." This is where many of us feel we can intuitively switch to different ingredients, try grain-free diets, or avoid a certain form of treat. These methods do not constitute a proper elimination diet and may result in worsening of symptoms or a delay in diagnosis and treatment for your pet.
Why? A dog's immune system that is allergic to chicken, for instance, might also react to duck as an ingredient. It may react to lamb if the dog has a beef allergy, etc. Choosing ingredients that are nonreactive for your dog is difficult to impossible. And we must consider the diet as a whole, including all treats, chews, people food, even flavored medications! Food allergy diets do not work by special ingredients contained in the food. They help by removing those ingredients. If we place a dog on an elimination diet, but still offer their favorite treat or flavored medicine, we will counteract the whole intention of the elimination diet.
The best test for a food allergy, in my experience and as recommended by dermatologists, is a Hydrolyzed Protein diet. Protein is the culprit in the majority of food allergic dogs. The most common proteins associated with allergic reactions in dogs weigh more than 20 kDa. The process of hydrolyzing protein will result in protein sources weighing less than 10 kDa. At this size, the immune system fails to recognize the protein as an allergen, therefore does not react to the food.
This type of diet must be fed exclusively, at least during the diagnostic phase. Food trials can take from six to 13 weeks to see definitive remission of symptoms. At that point, your veterinarian can discuss challenging the diet by adding in certain ingredients, one at a time, to monitor for reaction. This helps to identify the exact cause(s) of the allergic reaction.