By The Farmer's Dog | April 22, 2020

Allergies are yet another malady that people and dogs share, and they can make dogs as miserable as they make people.

Your dog’s allergies can also be tough on you—they can require some trial and error to diagnose and eliminate. Here, we’ll run down the symptoms, management, and treatment of allergies in dogs, and the role food can play.

But first, let’s back up and learn the basics.

What is an allergy?

An allergic reaction occurs when a dog is exposed to a foreign, normally benign, substance and their immune system goes into overdrive. The dog’s immune system releases antibodies and inflammatory substances as it attempts to eliminate the invader, even though the substance itself may not be harmful.

Take a common seasonal allergy like tree pollen. In the spring, trees release fine pollen that people end up breathing in. Your body might mistakenly interpret this pollen as a dangerous invader (like a parasite or bacterium), and launch an all-out attack against it. In humans, this results in cold-like symptoms as your body tries to flush out the enemy (weepy eyes, sneezing, sniffling, etc.). This type of allergic response is often termed hay fever. It’s important to note that in dogs, the environmental allergen actually causes a reaction through the skin; they don’t need to inhale it. That’s why it is important to bathe and wipe the paws of dogs exposed to environmental allergens.

What are the different types of allergies in dogs?

Dogs can suffer from many different types of allergies, and different allergies cause different symptoms. Three of the most common types of allergies seen in dogs include the following:

Environmental allergies (Atopy): Dogs with environmental allergies can react to a wide variety of substances found in the environment, including grasses, pollens, dust, mold, smoke, and more. Common signs of environmental allergies include itchy skin (called allergic dermatitis), hives, hot spots (skin infections), chronic ear infections, and sneezing.

Flea allergies: Some dogs are allergic to flea bites, suffering from severe itching and hair loss from even just one bite from one of these parasites. Flea allergies are usually easy to diagnose (if fleas are visible on the dog). They can be resolved by eradicating fleas from the dog and the home.

Food allergies: A food allergy, also called a food hypersensitivity, occurs when the dog’s immune system sees a food protein as a foreign invader and overreacts. The exact incidence of food allergies in dogs is unknown but research indicates it is infrequent compared to environmental allergies. With food allergies, dogs can be allergic to the proteins or glycoproteins of one or more food ingredients, commonly meat or carbohydrate sources.

The most common symptoms of food allergy can be similar to the symptoms of environmental allergies and include:

Itchy skin
Hives
Hair loss
Hot spots (skin infections)
Paw infections
Ear infections
Vomiting and diarrhea (more often associated with food intolerances)

Overall, the biggest sign of allergies is itching, no matter what the underlying cause is. Secondary to the itching, dogs experience hair loss, and skin and ear infections.

In addition to itchy skin, chronic ear infections are a common secondary sign of allergies in dogs. When the ear canal becomes inflamed and moist, overgrowth of bacteria and yeast can result, leading to ear infections. Signs of ear infections in dogs include frequent head shaking, scratching at the ears or rubbing the face on carpet (often while whining because ear infections are itchy and painful), and discharge and/or a foul odor coming from the ear canal.

Some dogs also have food intolerances, incorrectly called food sensitivities as they do not involve the immune system. Although these are not true allergies, they can still cause similar symptoms as food allergies, although food intolerances more often present as diarrhea and/or vomiting. A food intolerance could include poisoning from consumption of things that are toxic to dogs, like chocolate or onions, or a reaction to gulping down garbage. The general term “adverse food reaction” might be used when it is not known if a dog suffers from a food allergy or food intolerance. In dogs, allergies and intolerances are more formally known as cutaneous adverse food reactions (CAFRs).

It seems as though allergies are everywhere, and that they’re on the rise in dogs. Insurance companies like Nationwide report that skin allergies are the number one issue that prompts vet visits. But food allergies are actually still relatively uncommon, and certainly much less common than food intolerances.

Some sources indicate that (diagnosed) food allergies account for about 1% of skin conditions in dogs, and for the conditions associated with allergies, 10% are diet-related. One 2017 research review noted that “among dogs presented to their veterinarian for any diagnosis, the prevalence (of CAFR) was 1 to 2% and among those with skin diseases, it ranged between 0 and 24%.”

Although food allergies are less common than environmental allergies, they can be challenging for pet owners. For dogs that are diagnosed with food allergies, finding a diet free from allergic ingredients is life-changing for the dog.

A study published in 2016 that showed the most common triggers for food allergies in dogs are beef, dairy products, chicken and wheat. And while any individual dog can be allergic to almost any food ingredient or ingredients, many vets point to animal proteins as the most common culprits.

How are allergies diagnosed in dogs?

Unfortunately, there is no one perfect test that can definitively diagnose food allergies in dogs.

As there is for humans, there is a blood test for diagnosing allergies in dogs. A majority of veterinarians, veterinary dermatologists, veterinary internists, and veterinary nutritionists, though, do not recommend blood testing due to the questionable validity of these tests.

For environmental allergies, intradermal testing is recommended. Intradermal allergy testing involves injecting small quantities of allergens under the patient’s skin. This is typically performed under sedation or anesthesia. Up to 60 small injections can be given in a single area of the body (typically the abdomen) with a small sample of each allergen just under the skin. A “positive” response to an allergen appears as a visible swelling. This swelling forms at the injection site and is usually observed with 20 minutes of injection. If such a swelling does occur, the patient is assumed to be allergic to that specific allergen.

The dietary elimination trial

Ultimately, just as in humans, the gold standard for food allergy testing is something called a dietary elimination trial. You eliminate most food ingredients from your dog’s diet and wait for the allergic symptoms to subside. In practice, this process can be a lot to manage.

An elimination diet begins with creating a thorough diet history of all the food, treats and supplements your dog has been consuming, past and present. Since protein is the allergen, you need to find a protein source your dog has never been previously exposed to (chewable medications, flea, tick and heartworm products must also be changed to topical as they are typically flavored with proteins).

This process can be difficult as it requires knowing exactly what your dog is eating, and many pet diets may contain ingredients not listed on the label. One recent study, cited “concerns that commercial pet foods might contain unlisted food sources that could negate the usefulness of performing food trials, and concluded that “the mislabeling of pet foods appears rather common.”

A dietary trial typically lasts a minimum of six weeks but ideally up to 12 weeks. If the dog also has environmental allergies you may see only a partial response.

Once your dog has reached a baseline, you can start adding other food ingredients back into their diet, one by one (called a challenge). If the dog’s symptoms return, you’ll have identified the culprit ingredient and can then choose an appropriate diet that does not contain the ingredients your dog is allergic to. Some dogs are allergic to just one food; others are allergic to more than one.

“Once a food allergy is definitively diagnosed, it is reasonable to add back in common protein sources one by one to determine which triggers a dog’s allergies,” says Jennifer Coates, DVM. “Any diet that does not include these triggers should be appropriate for long term feeding,” she says. Some vets note that many people don’t add back in different proteins once they start the hypoallergenic diet, and just keep their dogs on the hypoallergenic diet if it is working well.

How are food allergies treated in dogs?

There are really only two ways to deal with your dog’s food allergies. You can either treat the symptoms, or you can treat the root cause.

To treat the symptoms, your vet might prescribe a range of different prescription medicines. Anti-diarrheal, antacid, probiotic, and antiemetic (anti-nausea) medication can ease your pup’s stomach upset. Or, if they’re experiencing skin discomfort, antihistamines and skin-soothing prescriptions may be helpful. If a bacterial or fungal infection develops (which can result from their constant scratching), antibiotics and antifungals may be appropriate. Such treatments can help your dog feel better (which is important!), but they’re not addressing the root of the problem.

What’s the best dog food for allergies?

If you want to fix your dog’s food allergy for good the most reliable solution is to find out what they are allergic to and stop feeding it to them. While most food allergies will disappear if you’ve been successful in this, it’s worth noting that many dogs have both food allergies and environmental allergies. So you may greatly improve signs of allergies with diet change, but dogs still may have some signs if there is an environmental component.

Finding a diet that is compatible with your dog’s food allergies is important, and hard to do with dry, processed food. Most commercial dog foods contain a long list of ingredients, and it’s not always clear what all of them are. “Keep in mind that you have to closely read the ingredient list on over-the-counter foods since a diet that is called ‘lamb and rice’ may still have chicken in it, for example,” Dr. Coates says. “Over-the-counter foods may also contain trace amounts of ingredients not on the label that can trigger a dog’s allergies.” One study of commercial, over-the-counter processed dog food showed that unlisted ingredients appeared in 13 out of 14 brands.

When shopping for food for your allergic dog, look for minimally processed, simple, limited-ingredient diets that clearly state the exact ingredients on the label (for instance, “turkey” not “poultry,” or “meal”).

Although it can be tempting to cook your own dog food at home, finding a recipe and cooking a complete-and-balanced diet for your dog is challenging. In fact, recent research found that 95% of recipes online were lacking in crucial nutrients for dogs. However, fresh food diets offer many health benefits, especially for dogs that have been dealing with allergies. A simple way to feed a fresh food diet is with a subscription to a fresh food plan that delivers fresh food with the correct balance of vitamins and nutrients made from veterinarian-approved recipes.

Food Allergy Management

Any pet owner with an allergic dog can attest to the fact that there is rarely a quick, one-and-done solution; managing allergies can be a frustrating process. “Allergies can worsen, and dogs can become allergic to new things over time, so it is extremely important to maintain good communication with your veterinarian,” Dr. Coates says. If your dog’s symptoms aren’t responding to treatment, be sure to call your veterinarian.

This article was vetted by a vet.
Reviewed by:
Alex Schechter, DVM, Founding Veterinarian at Pure Paws Veterinary Care.