Food Allergies in Dogs

by Dr. Laci Schaible, DVM

When my friend Jana Rade asked me to help write on food allergies in dogs, I was delighted to. I know Jana and her dog Jasmine have been to hell and back when they were struggling with what would take years to diagnose as Jasmine's food allergies.

Food allergies are gaining more and more recognition, both by pet parents and by veterinarians.

I am happy to take this opportunity to explain just what they are and how a diagnosis can be reached.

A food allergy is a reaction to the food by the body's immune system.

Food allergies are not food intolerances despite the common confusion. 

Day 296 Oct 13

Food allergies are among the top three most common cause of allergies in dogs, at least allergic itching that is. The others are flea allergy dermatitis and canine atopy, both of which are far more prevalent than food allergies, which compromise approximately 10% of all dog allergies.

Unlike canine atopy, food allergies are not seasonal, however, when pets present with GI symptoms they may wax and wane to some extent.

Most often, a protein in the food causes the immune system to react.  

Often the protein source is animal-based, such as meats eggs, or dairy, but sometimes a carbohydrate source can be involved too.  The most common ingredients that dogs have allergies to include beef, chicken, eggs, milk, fish, horse meat, potatoes, soy, corn, wheat gluten, or additives.

The most common clinical signs are severe itching, scratching, and chewing.  

Sometimes it may be accompanied by the small red bumps, pustules, and infection.  In dogs, the paws, flank, groin, neck, and ears are commonly affected.

Dogs with food allergies often suffer from recurrent ear infections.

These signs are usually year-round, unlike canine atopy.

Other times, food allergies present with gastrointestinal components instead of the skin component. 

GI signs include chronic vomiting, diarrhea or loose stools, belching, and frequent bowel movements and/or flatulence.  GI signs do fluctuate a bit more than skin problems, and a long history of "troubled GI system" is not uncommon.  Dogs may suffer from both skin and GI symptoms.

Since food allergy is less common than canine atopy and flea allergy dermatitis, the vet often starts by treating the easiest of those--flea allergy dermatitis--by recommending topical flea meds.  This is reasonable in my expert opinion.

No single specific test can diagnose a food allergy.  

Allergen blood testing is available, but it is more appropriate for canine atopy and is not a reliable way to identify what food ingredients your dog may be allergic to.

The diagnosis is slowly made by placing your pet on a trial diet in which you are introducing a new, highly digestible protein source, and/or carbohydrate source, with no food additives.  

You, in essence, are eliminating the potential offending allergens and thus it is often called an "elimination diet."

You can prepare this diet at home if you consult with a veterinarian with expertise in nutrition.  

Usually, it is advised to select a single novel protein (such as duck, rabbit, kangaroo), a novel carbohydrate source (such as snow peas), and a source of fat.  If your pet responds and the itching decreases, it will be of crucial long-term importance to ensure the diet is balanced and complete.

Commercial diets with novel food sources are available, but in my opinion, if you want a commercially prepared diet, it is wiser, simpler, and more affordable to choose a hydrolyzed diet. 

Hydrolyzed protein diets contain proteins that are broken down into pieces too small to to fit into the receptors that stimulate the pet's immune system.  In other words, they sneak right past the dog's allergic alarm system due to their tiny size.  
These diets are already complete and balanced for adult dogs.  It is rare for a kitten or puppy to develop true food allergies, as the dog has to be exposed to the allergen repeatedly, and it is repeated exposure that intensifies the allergies and their symptoms.

Itching may start to decrease within a couple weeks, but in most cases, it does take longer (around 6 weeks).  

The test diet should be fed for two to four months. For dogs that respond positively, the diet should be continued provided it is balanced and complete.

The pet parent must remember that table scraps, treats, chews, and flavored medications (such as heartworm meds) must not be given not only while the pet is on the trial diet, but no offending allergens can be given the rest of the pet's life after the offending allergen is identified.

The prognosis for pets with food allergies is great as long as the pet is not re-exposed to the food ingredient(s) that triggered the immune response initially.  

The pet owner must be vigilant to maintain the strict diet.

Though it is indeed a very frustrating diagnosis to arrive upon, once it is made the pet parent can breathe a sigh of relief knowing that if the offensive allergens are avoided there pet will no suffer the skin or GI side effects associated with food allergies again.


Dr. Laci Schaible, DVM is a veterinarian in Pennsylvania.  With her husband Dr. Jed, also a veterinarian the two have founded, the world's first and only site that allows pet owners to connect with unbiased and licensed veterinarians 24/7.  If you have a question about your pet, you can ask a vet online and get an answer immediately.

Articles by Dr. Laci:
A Tale of Many Tails—and What Came Out From Underneath Stories from My Diary-rrhea (part I)
Acute Small Intestinal Diarrhea
Acute Large Intestinal Diarrhea (Acute Colitis)
Chronic Large Intestinal Diarrhea
Chronic Small Intestinal Diarrhea

Related articles:
Why Is My Dog So Itchy? Top 5 Causes Of Itching In Dogs


  1. Thank you Jana for publishing my article on your blog. I hope that it might set off an alarm if owner pet parents suspect or have been told their dog has a "sensitive stomach." Sorry you and your family went through that agony with your sweet girl.

  2. Dear Dr. Laci

    Thank YOU for writing it for me. Yes, it is unforgivable that nobody bothered to look past their "sensitive system" diagnosis. Luckily we now have a vet who'll go as far as needed. And not that he'd have a choice, I'm keeping him on his toes :-)

  3. Hi Y'all,

    Great post.

    As I also know, from Hawk's allergies, both food and stuff like grass, that only by changing vets do we find the vet who is really interested in the dog's welfare.

    I think some vets thought we weren't properly caring for our dog.

    BrownDog's Momma

  4. I agree. Sadly there are some out there who lack either the drive, care or expertise or all of the above.

  5. Yeah, I agree w/ Jana...I once encountered a vet who would just give us expensive medicines but are not really working. Luckily my dog's case is not as sensitive as yours. Great article, thanks for sharing!


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