Food Allergies in Dogs: Allergies Are Not the Same as Food Intolerance

Food allergies in dogs are gaining more and more recognition, both by dog parents and by veterinarians.

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

What are canine food allergies and how to reach a diagnosis

A food allergy is a reaction to food by the body’s immune system. Food allergies are not food intolerances despite the common confusion.

Food allergies are among the top three most common causes of allergies in dogs, at least allergic itching. 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, GI symptoms may wax and wane to some extent.

The most common allergens are proteins

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. However, sometimes a carbohydrate source can be involved too.  The most common ingredients dogs have allergies to include beef, chicken, eggs, milk, fish, horse meat, potatoes, soy, corn, wheat gluten, or additives.

Skin-related symptoms of dog food allergies

The most common symptoms of canine food allergies are

• severe itching
• scratching
• chewing at skin

Sometimes it may be accompanied by

• small red bumps
• pustules
• secondary infections 

In dogs, the commonly affected parts of the body are

• paws
• flank
• groin
• neck,
• and ears

Dogs with food allergies often suffer from recurrent ear infections. These signs are usually year-round, unlike canine atopy.

Gastrointestinal symptoms of dog food allergies

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

Gastrointestinal signs include

• chronic vomiting
• diarrhea or loose stools
• belching
• frequent bowel movements
• flatulence

GI signs fluctuate more than skin problems, and a long history of “troubled GI system” is not uncommon.  Dogs may suffer from both skin and GI symptoms.

Food allergies in dogs are less common than canine atopy

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.

Diagnosing food allergies in dogs

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 involves placing your dog on a trial diet in which you are introducing a new, highly digestible protein source and/or carbohydrate source, with no food additives.

Elimination diet

You, in essence, are eliminating the potential offending allergens; 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.  

The typical recommendation is to use a single novel protein (such as duck, rabbit, kangaroo), a novel carbohydrate source (such as snow peas), and a source of fat.  If your dog 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. Still, 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

Hydrolyzed protein diets contain proteins that are broken down into pieces too small to fit into the receptors that stimulate the dog’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. Therefore, it is rare for a kitten or puppy to develop true food allergies. However, the dog has to be repeatedly exposed to the allergen, which intensifies the allergies and symptoms.

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

How long an elimination diet should last

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

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

Prognosis and final notes

The prognosis for dogs with food allergies is excellent if the dog is not re-exposed to the food ingredient(s) that initially triggered the immune response.

The dog owner must be vigilant to maintain a strict diet.

Though it is indeed a very frustrating diagnosis, once it is made, the dog parent can breathe a sigh of relief knowing that if the offensive allergens are avoided there, a dog will not suffer the skin or GI side effects of food allergies again.

Puppy diets and onset of allergies and atopy in addulthood

Researchers at the University of Helsinki took a closer look at the relationship between allergies in dogs and puppyhood diets. Does it surprise you that what a dog eats as a puppy might affect whether they develop allergy and atopy later in life?

During the study, the researchers evaluated 4022 dogs and their puppyhood diets. What did they find?

Consumption of at least 20% of the puppy’s diet as raw food, or less than 80% of the puppy’s diet as dry food, associated with a significant decreased prevalence of allergy and atopy related skin symptoms in adult age.

ScienceDaily

Conversely, dogs whose puppy diets contained no raw food or those whose diets consisted of 80% or more dry food had a significant increase in the prevalence of allergies later in life.

Combining dry kibble with other commercial foods such as canned or moist also increased the odds of allergies. On the other hand, diets consisting of at least 20% of raw foods improved the dog’s future health. That applies even to puppies who supplemented their diets by eating dead animals outside.

While the study only suggests and does not prove the relationship between puppyhood diets and adult dog allergies, it is something to think about.

Further reading: A puppy’s diet seems to be a sig­ni­fic­ant factor in the de­vel­op­ment of al­lergy and atopy re­lated skin symp­toms in adult dogs

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

Further reading:
Diagnosing Food Allergies in Dogs