Dial into food allergies in pets

Veterinary teams are the first line of defense as pet owners consult with their veterinarian about food allergy in dogs and cats. Clients are often distressed when their pets are itchy and uncomfortable. But with your team's support, you can help guide pet owners through the process of discovering the source of their pet's problem and offering relief.

It's roughly estimated that food allergy potentially causes about 10 percent to 15 percent of itchy skin disease, or pruritus, in dogs and cats, or up to 30 percent of non-seasonal dermatoses. It may also cause gastrointestinal problems, such as vomiting. The itchy condition may encourage dogs and cats to scratch. This makes them susceptible to secondary opportunistic bacterial infection, which often exacerbates the allergic response and pruritus.

Although the incidence of food allergy in pets is likely about the same as it always has been, veterinarians are recognizing it more. This is because veterinary teams are more aware of food allergy and food intolerance as a common problem and have more options for diagnosing the condition.

Anything that a pet eats can cause food allergy, but food proteins are the most likely. Common culprits include fish, beef, chicken, cow's milk, eggs, soy, and wheat protein. Other meat protein sources, previously considered novel in pet diets, have also been shown to cause allergy in both dogs and cats. These include lamb, whale, rabbit, and pork, just to name a few.

Several years ago, lamb wasn't a common pet food ingredient. Now it is, and it's common for pets to show an allergic response, as they can to other meat and plant proteins.

Meat proteins are the most common cause, but plant proteins can be a culprit too—especially soy, wheat, and corn gluten. These aren't bad or unhealthy ingredients, but they may cause food allergy in some pets.

One key role for technicians is taking a thorough history. Sandra Grable, CVT, a dermatology technician at the University of Illinois Veterinary Teaching Hospital, says it's important to ask leading questions to help pet owners remember items they may not think are important—or ones they forget to tell you. These include flavored medications or supplements, rawhides, or other flavored chew toys.

Food for thought

Intradermal skin testing and serum testing aren't accurate diagnostic tests for food allergy. The only way to determine whether a dog or cat is food allergic or intolerant is by eliminating the inciting food ingredient from their diet. This process requires help from the entire team and an owner committed to complying with the dietary recommendations.

Once you know a pet's complete dietary history, the tried-and-true method for diagnosis is to put the pet on a novel protein-limited ingredient elimination diet for at least two to four weeks, and preferably 10 to 12 weeks. The goal is to choose a diet that contains only proteins that the pet has never been fed before, and therefore never sensitized to. There are many commercially available canned and dry diets that contain more unusual ingredients that range from sweet potato and duck to potato and venison, pumpkin and rabbit, salmon and green pea, and so on. It's important to understand that the veterinarian works to select foods with ingredients that are novel or foreign to a particular pet's dietary history and less likely to produce an allergic response. The ingredients in these diets are not "hypoallergenic." A food trial is a diagnostic tool to test for food allergy or intolerance. Owners need to know that their complete compliance is the only way to ensure accurate results.

An alternative to the limited-ingredient, novel-protein diets is the newer hydrolyzed protein therapeutic diets. These are composed of proteins that have been essentially shortened, pre-digested, of minimal amino-acid length and composition, which then fool the gut and the immune system to accept them. These diets work well for some pets and are very convenient for owners. However, as they are not elimination diets, if the pet improves, the client will need to continue the use of the diet indefinitely. Other considerations such as cost and palatability must be weighed for each case.

If pet owners prefer, they may consider a homemade diet during the elimination trial. Owners should be cautioned that in addition to utilizing a novel protein and limited ingredients, preparing a diet that provides complete and balanced nutrition is necessary.

The key to a successful elimination dietary period is compliance. Beyond providing the new diet at meal times, pets must avoid treats and flavored medications that contain a potential allergen.

Novel protein diets are more expensive than most over-the-counter diets, Grable says. Pet owners who comply with the trial the first time will avoid the frustration and cost of having to restart the trial.

Good as new?

If the pet suffers from a food allergy or intolerance, then the skin condition or vomiting should begin to clear up within several weeks after beginning the elimination diet. At this stage, to try and identify the specific cause of the allergy, the owner and veterinarian may decide to challenge the pet with the previous diet or individual ingredients. But, for many pet owners, once the allergic response is resolved they are happy to permanently change to one of the novel foods that work.

Hopefully the pet won't experience another bout of food allergy or intolerance, but it's a good idea to caution pet owners that over time, the pet may develop an allergy to the new diet, necessitating another carefully selected dietary trial.

Words of encouragement can go a long way to helping clients during a food trial, Grable says. For example, you might say, "I understand that it's hard to deny Fluffy the treat that she so desperately wants. But it's in her best interest to stick to the plan."

During recheck appointments, Grable says the technician's role includes taking a complete and thorough history, including asking how the animal has responded to the dietary change.

Ed Kane, PhD, is a researcher and consultant in animal nutrition. He is an author and editor on nutrition, physiology, and veterinary medicine with a background in horses, pets, and livestock. Kane is based in Seattle.