Is your pet having skin, respiratory or gastrointestinal issues? Are these problems allergies or some other reaction? Are your pet's allergies caused by the food you are feeding them? 

The answer is not simple because all dogs/cats are different, and your pet's food requirements may change based on their age, health or other conditions. We know that some pets can eat the same diet for years with no negative effect and other pets may develop an intolerance or allergy to a food that they have been successfully eating for years. Food allergies and intolerance can suddenly appear at any age.

True food allergies are relatively rare and what many pet owners assume are allergies are actually food intolerances. Both adverse reactions share many symptoms, but allergies are usually from protein sources or environmental and are based in the immune system whereas intolerances are generally gastrointestinal and do not involve the immune system. Allergy symptoms generally manifest in skin, respiratory, vomiting, diarrhea or other gastrointestinal issues and can be life threatening. Food intolerances can also have these symptoms but tend to be less severe and both can affect skin, paws or itchiness.

Allergies require the pet to be exposed to the allergen at least for some period of time for the body to identify it as an allergen which is why the most common foods identified in food allergy diagnosis are beef, dairy, chicken and wheat in that order.  BCM Vet research. This is because these are the most common ingredients used in pet foods over the last 20 years. As the pet food industry evolves, we may see other ingredients emerge higher in the list of common allergens.


It is very difficult to diagnose allergies, especially food allergies. An elimination diet requires severely limiting your pet’s food sources to only 1 protein and 1 grain along with the required vitamins to maintain their health for a  minimum of 8 weeks. Keeping to a restricted diet can be tricky because commercial pet food is made in plants where a limited ingredient food can pick up trace amounts of allergens due to the manufacturing process. Even foods labeled as limited ingredient or a specific protein, can contain undesirable ingredients for a strict elimination diet. If your vet prescribes an elimination diet, it is best to use a food recommended by your vet. It takes months to see the results from an elimination diet and can often be deceiving if your pet’s allergic reaction is because of some other allergen such as pollen or other environmental issues.

Food intolerances may be more difficult to isolate as they can occur with foods your pet has been eating for a long time or can stem from secondary ingredients, grains, preservatives, oils and fats or other fillers. A grain free or limited ingredient diet may still contain a substance that your pet's system can no longer tolerate. Dairy is often more of a food intolerance than an immune response allergy.

Environmental allergies can have a broad range of interior or external sources. Pets may develop allergies to carpet fibers or foam fillers in dog begs or upholstery. Or symptoms only occur on a seasonal basis. For example, your pet is fine in the winter but starts going outdoors more in the Spring and starts itching. Is it fleas? Is it pollen? Is it something that is outside but not inside? Using a journal over a long period of time can expose environmental, food or treat trends.


Although true food allergies are somewhat rare, it does not hurt to change your pet’s protein source to see if the symptoms go away. Most vets recommend removing chicken first since it is often included as a secondary ingredient even in foods labeled as a different protein. Switching to a brand that has as few ingredients and preservatives as possible could eliminate other ingredients that might be problematic. It is possible for your pet to develop an allergy to the new protein so proceed carefully by introducing the new protein gradually over a few days or weeks to see how the new food is tolerated. Consider changing to an alternative protein since beef, dairy, eggs are all common in commercial dog food and could be the source of the problem.

Alternative proteins

Pet food manufacturers are widening their variety of protein sources. We now see brands with turkey, lamb, fish, pork, duck, rabbit, Guinea fowl, bison, venison, goat, crickets and in some countries, kangaroo. Look for foods with limited ingredients vs grain free. Many manufacturers are producing foods with short ingredient lists which is helpful if trying an elimination diet.  

Although grains are generally less likely of a problem than proteins, if you see wheat, soy or corn in the ingredient list, then perhaps consider a grain free brand as these grains are often causes of food intolerance. Most starches in kibble contain protein, such as potatoes, chick peas, pea starch and are used to boost the total protein of dried kibble. In severe cases, switching to canned, raw or frozen food may reduce the amount of starch-based proteins.

“Hypoallergenic” foods typically are sold by vets and are foods that have proteins that have been chemically “split” (hydrolyzed) into their basic amino acids such that the protein is not detectable by the body. Don’t forget about treats or bones. Read labels very carefully and restrict all food containing the target protein.

Do not try to treat your pet's allergies or food intolerance yourself without consulting your veterinarian because a collection of many symptoms may be a larger health problem in disguise. Medications or immunity issues may also be factors and your vet is your partner in helping your pet live a long and healthy life.