Food allergies in dogs: Vet's guide to symptoms and treatment

food allergies in dogs
(Image credit: Getty Images)

If your dog has been an itchy mess during all seasons of the year, it is possible that a food allergy is to blame. Skin problems are one of the most common reasons why dogs are brought to the veterinary clinic every year and many pet owners are all too familiar with their dog’s constant licking and scratching.

Although food allergies are much less common in dogs than pet food ads would have you believe, they are still a significant cause for concern. It’s worth considering the best dog food for allergies if your vet has diagnosed your pet with the condition. 

Food allergies can leave your dog’s skin itchy, red, irritated, and uncomfortable, and can also lead to digestive problems such as diarrhea, flatulence, and weight loss. If you suspect that food allergies may be affecting your pup, read on to learn more about this important canine condition and what you can do to help your dog.

 What is a food allergy? 

A food allergy, better defined as an “adverse food reaction”, is an abnormal response to the ingestion of a particular food or food additive.  The body incorrectly identifies the food molecules as an antigen, or a threat, and mounts an immune response against them, leading to symptoms like itchy skin or diarrhea in dogs.  

Food allergies most often develop after prolonged exposure to one type of food.  In dogs, the most common food allergens are beef, chicken, lamb, and wheat.  Allergies to soybean, milk, eggs, corn, walnuts, and possibly peanuts have also been reported.  Dogs that have developed an allergy to one type of food may also develop allergies to additional foods in the future.   

A chocolate lab eating from dish

(Image credit: Getty)

Symptoms of food allergies in dogs 

Food allergies most commonly affect the skin in dogs, and one of the most common symptoms of food allergies in dogs is itching, often occurring year round. Dogs with food allergies may also have recurrent skin infections, hair loss from frequent scratching or licking, and pustules, crusting, or excoriations of the skin.  

Many dogs with food allergies also have ear infections, often recurrent.  However, other conditions, such as Canine Atopic Dermatitis (CAD) can also present with the exact same symptoms, so it is important not to self-diagnose your dog with food allergies based on appearance alone. If your dog displays any of these symptoms, it is essential to see your veterinarian for a proper diagnosis and appropriate treatment.

Gastrointestinal symptoms of food allergies in dogs 

Although skin symptoms are the most common manifestation of food allergies, some dogs do display gastrointestinal symptoms, or a combination of both skin and gastrointestinal symptoms. Dogs with gastrointestinal symptoms typically display signs such as diarrhea, increased number of defecations in a day, flatulence, vomiting, drooling, weight loss, and abdominal discomfort.  

As with skin symptoms, these gastrointestinal symptoms can also be caused by other conditions, so it is important to see your veterinarian if you notice any of these signs or suspect your dog may have food allergies. Your veterinarian will help you take the appropriate steps to diagnose your dog with food allergies. 

Diagnosing food allergies in dogs 

 Although many companies claim to offer blood, saliva, or hair sample tests to diagnose food allergies, none of these tests are actually reliable.  The only way to accurately diagnose food allergies is by performing an elimination diet trial.  This involves putting the dog on a strict diet based on either a novel protein – something the dog has never had before – or a hydrolyzed protein, in which the proteins are broken down into smaller fragments.  

The dog must eat this diet and no other foods or treats for a minimum of 8 weeks.  If the patient’s symptoms have improved during the 8 week diet trial, then a diet challenge is performed.  This involves reintroducing the dog’s original diet to see if the symptoms return.  If the symptoms return within 14 days of restarting the original diet, the patient is diagnosed with a food allergy. 

dog getting checked by vet

(Image credit: Getty Images)

Treating food allergies in dogs 

Unfortunately, there’s no cure for food allergies in dogs, and no simple pill to fix the problem, either. If your dog is diagnosed with food allergies, he will need to eat a special diet for the rest of his life. In some cases, it is possible to identify which specific foods the dog is allergic to by performing diet challenges with different ingredients.  

In most cases, we never know for sure exactly which ingredients the dog is allergic to. These allergic dogs are treated by feeding a prescription veterinary hypoallergenic diet for the rest of the dog’s life.  This decreases or often even eliminates the symptoms of food allergies, allowing the patient to live a normal, comfortable life.

Over the counter diets claiming to be limited ingredient, novel protein, or hypoallergenic generally do not work well for these patients. That’s because these diets are made in facilities that also process regular dog foods, and cross contamination is common.  To ensure your dog is getting a truly hypoallergenic diet, it’s best to stick with the food recommended by your veterinarian, veterinary dermatologist, or veterinary nutritionist.


Food allergies in dogs inevitably prove to be a tough predicament: you obviously can’t stop feeding your dog, but food is the very thing causing your dog’s discomfort!  Fortunately, once your dog has been diagnosed with food allergies following a strict 8 week elimination diet trial, the management of food allergies can be quite simple.  

Your dog will need to eat a prescription hypoallergenic diet for the rest of his life.  With patience and a bit of luck, many owners of allergic dogs are also able to find some healthy fruits and veggies that they can use as treats, that their dog won’t have an allergic reaction to.  So although food allergies can be a tough diagnosis to hear, your dog can still have a long, full, and happy life with the help of your veterinarian and, of course, you!

Elizabeth Racine, DVM

Dr. Elizabeth Racine is a small animal general practice vet covering all things pet health and wellness.  Her special interests include veterinary behavior, nutrition, and internal medicine.  As a freelance writer, Dr. Racine has written content for major companies in the industry such as the American Kennel Club, Merck Animal Health, Bayer PetBasics, Elanco, and CareCredit.  In her free time, Dr. Racine enjoys playing trampoline dodgeball, hiking with her beagle Dasher, and spending time with her three mischievous cats.