Food Allergy

Food allergies are a complex topic and difficult to summarize, but we wanted to touch on some important things to consider with respect to food sensitivities in our pets. These days, the internet and marketing are very effective in selling us on certain diets, but facts can be hard to come by.

Food allergy is not common in our pets, but some breeds can be more prone, such as Labradors and German Shepherds. The allergy can be expressed either in the gastrointestinal tract where it will be apparent with vomiting and diarrhea. It might also cause skin symptoms such as recurrent ear infections and itching. In cats, itching of the head and neck is associated with food sensitivity and in dogs, itching the ears, paws and rear end can be a clue.

In many cases, animals can show symptoms at a young age, 33% before their first birthday. With this being said, it can develop at any stage in their lives, even on a diet they have eaten for years. The itching tends to be non-seasonal, meaning it occurs year round and can be quite intense. Common sources of allergen can be chicken, beef, soy, fish and occasionally wheat and corn.

Diagnosing a food allergy can only be done with a hypoallergenic food trial. Hair and saliva tests are not reliable. While blood tests may have a place with other allergies, they are of no use in a food allergy. There are some new tests in development, but they are not commercially available as yet.

It is key to use a prescription diet when doing a food trial. Simply switching to a commercial grain free diet or a raw diet is unlikely to be successful. Recent studies have shown that raw diets may actually be more stimulating to the immune system. Commercial diets may claim to have certain proteins and non -grain ingredients, but there is a high risk of cross-contamination from other diets on the production line and no guarantee that what is on the list of ingredients is actually in the bag; they are free to substitute at any time. Studies have shown that some commercial diets claiming to contain certain proteins actually do not. Canned diets may also be less allergenic than dry foods, but that can be difficult when feeding a Labrador!

We have several options when it comes to trialling a new prescription hypoallergenic diet. Often it depends on the food sources the pet has already been exposed to – dogs tend to get more variety than cats! – so we might try to choose a novel protein/carb combo such as kangaroo/oats or venison/pea. Some proteins can cross-react; for example, an animal that is sensitive to chicken might also react to turkey or duck. We also have newer generations of hydrolyzed diets. These foods are proteins that have been broken down into smaller components, designed to be unrecognizable to the immune system. Since more and more proteins have entered the commercial space (lamb and rice was the original hypoallergenic diet!), the hydrolyzed diets are becoming a standard first choice in many cases. Sometimes it may take several different diets to truly assess if a diet is a component in a pet’s allergy symptoms.

The food trial generally lasts from 8 to 12 weeks and there are strict restrictions on just feeding the prescription diet and nothing else. If things are going well, the treats can be added back one at a time to assess whether they are a trigger or not.

The marketing push for grain-free is just that, a marketing tool. With recent concerns about grain-free diets possibly being linked to heart disease in some dogs, the overall advice is to feed a good quality dog food with unremarkable ingredients such as chicken, corn and wheat. If they are part of the small percentage that has a true food allergy, it gives us lots of options when trying new food and hopefully improving your pet’s comfort and health.

Written by: Dr. Adrienne Randall, Veterinarian