How to Tell if Your Dog Has Food Allergies

Jennifer Coates, DVM
By Jennifer Coates, DVM on Feb. 10, 2020

Food allergies in dogs can be tricky to identify. The symptoms aren’t what many pet parents expect, and there are a lot of myths out there about food allergies in dogs. True food allergies are not that common in dogs, for one.

Here’s how you can figure out if your dog has food allergies and what you can do about them.

Reasons to Suspect Dog Food Allergies

When people think about pet food allergies, they often jump to gastrointestinal issues. However, food allergies in dogs may or may not come with an upset stomach.

The most common symptoms of food allergies in dogs actually show up as reactions in their skin.

Skin and Ear Problems in Dogs With Food Allergies

Skin problems are common in dogs with food allergies. At first glance, this seems kind of odd, but it makes more sense when you think about how people react to food allergies.

Dogs with unchecked food allergies may also have trouble with their ears.

Some of the most common health issues associated with legitimate dog food allergies are:

  • Chronic itchiness

  • Skin lesions, especially when a dog is self-harming in an effort to scratch the itch

  • Frequent ear infections

Similar symptoms may be caused by environmental allergies to triggers like pollen, mold, and house mites, but these, at least to start with, are often seasonal.

For this reason, it’s important to track whether your dog’s symptoms ebb and flow with the changing of the seasons.

When Do Dog Food Allergies Develop?

It’s important to remember that food allergies can develop at any time. A food your dog has consumed for years with no troubles may suddenly cause an allergic reaction, or symptoms may develop soon after you change your dog’s diet.

How Are Dog Food Allergies Diagnosed?

Diagnosing food allergies in dogs isn’t always a straightforward process. It’s not like there’s a simple test that can instantly tell what your dog is allergic to or, if indeed, he has food allergies at all.

You have to start at the beginning, with the help of your veterinarian, to know for sure whether your dog’s skin or ear issues are caused by food allergies.

Rule Out Other Health Issues

Your veterinarian will take a full history on your pet and do a general exam.

Next, they will likely run tests to rule out conditions with similar symptoms like mange, ringworm, yeast infections, bacterial infections, flea infestations, and environmental allergies.

Ruling out those conditions comes first because true food allergies are relatively uncommon.

If there is no other apparent cause for your dog’s symptoms, your veterinarian may begin to suspect that food allergies are behind your dog’s itchy skin or ear infections.

Even if your vet finds a “reason” for your dog’s skin problems, they may still suspect that an adverse food reaction is at least partially responsible since, for example, yeast infections can develop as a result of food allergies.

Once a diagnosis of food allergies seems to be a reasonable possibility, your vet will recommend a food trial.

Starting a Food Trial

Starting your dog on a food trial means your pet will eat a prescription diet and absolutely nothing else for a couple of months to see if symptoms resolve.

If they do, some veterinarians will suggest going back to the dog’s old diet to see if symptoms return to ensure that the dog is truly allergic to one or more ingredients in their “regular” diet.

Evaluating a Food Trial: Food Allergies vs. Food Intolerance

Seeing results from the food trial are not a guarantee that your pet has food allergies. In some cases, you may find out that your dog has a food intolerance.

Food Allergies

Food allergies occur when the immune system responds inappropriately to something (usually a protein) found in the diet.

Instead of treating this perfectly innocuous substance as it should, the immune system treats it as a threat—an invader of sorts.

Food Intolerance

A food intolerance is different from an allergy in that the symptoms are not caused by an immune reaction.

In dogs, food intolerances typically cause tummy troubles; they may vomit or have diarrhea, be seriously gassy, or have a poor appetite.

Treating Food Allergies in Dogs

The only effective way to treat a food allergy in dogs is to change their diet.

While grain-free foods are often touted as good for food allergies, science tells us that protein sources are more likely to be the culprit. According to a study published in 2016, the top three most common causes of food allergies in dogs are beef, dairy, and chicken.

Diets for Dog Food Allergies

Here are a couple of different approaches to treating food allergies in dogs.

Novel Proteins

This approach involves feeding proteins that your dog has likely never been exposed to in an effort to avoid an allergic reaction. Rabbit, venison, and other novel ingredients are used in place of more common protein sources. Allergy-friendly foods must be completely free of your dog’s triggers.



Hydrolyzed Proteins

Rather than changing which proteins are used, hydrolyzed protein prescription diets break proteins down so that the immune system no longer recognizes them as a threat.

Treating Itchy Skin and Ear Issues Caused by Food Allergies

The only way to treat a food allergy is to remove the offending food from the dog’s diet, but there are options for temporarily treating the symptoms caused by food allergies.

Oral and topical medications are sometimes prescribed to help minimize itching. Any secondary problems, like skin or ear infections, will also have to be addressed.

If you’re concerned about any symptoms your dog is experiencing, or you’re simply wondering whether the food you’re offering is the best choice for your pet, speak with your veterinarian.

By: Jennifer Coates, DVM

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Jennifer Coates, DVM


Jennifer Coates, DVM


Dr. Jennifer Coates is an accomplished veterinarian, writer, editor, and consultant with years of experience in the fields of veterinary...

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