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Could My Pet Be Allergic to Their Food?

Reviewed by Amy Flowers, DVM on October 21, 2021
dog eating out of food bowl

Just like people, cats and dogs can have food allergies, too. And like humans, those allergic responses can range from itchy and irritating to severe and dangerous.

Food allergies in pets can begin at any age. They can start even if your cat or dog has been eating the same food for months or years.

Is It a Food Allergy

A food allergy happens because of a pet’s immune system. That’s what normally fights off germs and other things that could cause disease.

When a dog or cat has a food allergy, their immune system mistakes food for something harmful, then goes on the attack. That causes a reaction.

Common symptoms in cats and dogs

If your pet has a food allergy, you may notice:

Itchy skin: Also known as allergic dermatitis, this is the most common type of allergy in pets. Irritated, itchy skin can happen anywhere on your pet’s body. In cats, it often happens on the head and neck.

In dogs, it often happens near the:

  • Ears
  • Paws
  • Rear end
  • Stomach

Skin issues: Hives, also known as urticaria, may pop up 6 to 24 hours after your dog eats the food they are allergic to. If your dog has short hair, these itchy red bumps are easier to see. Otherwise, you may have to feel for them.

In cats, skin irritation may take longer to see. Small lumps filled with fluid may develop over a few months, but they usually don’t pop up overnight.

With itchy skin and hives, there are two side effects of the irritation:

  1. Your pet likely will scratch, bite, and lick the affected areas, which can lead to broken skin. If the skin is open, there’s a chance your pet could get an infection, which would need treatment.
  2. All that scratching can lead to hair loss.

Tummy trouble: Allergies may cause gastrointestinal issues, such as gas, vomiting, and diarrhea.

Swollen face: You may see swelling in your dog’s lips, eyelids, or ear flaps.

Chronic ear or paw infections: Repeated infections in your dog’s ear or paws may be a sign of a food sensitivity, not a food allergy.

There’s a difference between a food allergy and food sensitivity. For example, an allergy triggers an immediate immune system response. Food sensitivity doesn't. Your dog may have food sensitivity if they are having a gradual reaction to an ingredient in their food.

Common allergens for cats and dogs

When it comes to food, the most common culprits are:

  • Chicken
  • Beef
  • Egg
  • Fish (for cats)
  • Dairy products

Less common ones include:

  • Corn
  • Wheat
  • Rice
  • Barley
  • Oats

Talk to Your Vet

If you think your dog or cat may have a food allergy, make an appointment with your vet.

The more info about your dog or cat’s diet that you can share with your vet, the better. Once you have a better idea of what’s behind your pet’s allergy, you’ll be able to ease their symptoms and stop future flare-ups.

What your vet needs to know. Before your pet’s office visit, write down:

The symptoms your pet is having: A food allergy can affect pets in different ways. Share all the changes you’ve seen in your pet, even if you aren’t sure they’re linked. If you know the dates they started, jot them down, too.

The food your pet is eating: Your pet may eat the same food for up to 2 years before their immune system starts to have a problem with it. Make sure your vet also knows about any snacks you give your pet -- whether they’re from your dinner plate or bought at the pet store. Include any flavored toys and toothpaste your pet uses.

Drugs and supplements: Is your pet on any meds? Even if you give them herbal supplements or an over-the-counter product, tell your vet the name, the amount your pet takes, and when they started.

Other allergy triggers: Has your pet been exposed lately to fleas, pollen, dust mites, or grasses? These can all cause the same symptoms as a food allergy.

Getting a Diagnosis

Your vet may suggest:

Allergy testing: Just like in humans, figuring out a pet’s food allergy can take time. First, your vet may try to rule out other things that could lead to a dog or cat’s symptoms.

Elimination diet: The best way to figure out a food allergy is with one of these, which should only be done under the care of a vet or nutritionist, who may prescribe special food for your pet during the trial. It takes several steps:

  1. Switch your pet to a diet made of things it has never eaten. You might have to buy food from the vet or make it at home. For the next 10-12 weeks, nothing else that’s flavored can go into your pet’s mouth. Not food, not chew treats, not scraps from your dinner table, and not even medications that are flavored. If your pet’s symptoms clear up, that may mean it has a food allergy. But that isn’t settled yet.
  2. Now go back to your pet’s old diet. If the itchy skin or other symptoms come back, your pet probably does have a food allergy. But you’re still not finished.
  3. Switch back to the special diet from the first step and wait for the allergy symptoms to go away again. Now add one ingredient from the kind of food that your pet always ate, and then wait a while. If the symptoms don’t come back, your pet isn’t allergic to that. So add back another ingredient from the old diet. Keep doing that until you get to one that makes the symptoms return. That’s probably the culprit for the allergy.

It takes weeks or months to do all that. So your vet will probably want to start by checking for other conditions that could trigger the same symptoms.

You need the help of a professional with this. That's the only way to make sure you both find the cause of the allergy and do it in a nutritionally complete way.

Treatment

Most of the time, you can manage food allergies in cats and dogs by making changes to what they eat, so that they avoid their trigger food.

Your vet may prescribe medication to help ease symptoms while they figure out a long-term plan.

It’s rare, but a life-threatening allergic reaction can happen and your pet may not be able to breathe. If that happens, call an emergency animal hospital right away.

Other Things That Cause Digestive Troubles

Is there some kind of food that just doesn’t agree with you? The same thing can happen with your dog or cat. Maybe it’s eating something that has too much fat, for instance.

Vets call this food intolerance. The difference between this and a food allergy is that food intolerance doesn’t involve the immune system.

To figure out if this is what’s wrong with your pet, you’ll have to follow the same trial-and-error process as you would for a food allergy, described above.

Diarrhea and vomiting can also come from:

  • A virus
  • An infection
  • A parasite
  • A condition in your pet’s digestive system. One example is pancreatitis, which is inflammation in the pancreas, the organ that makes chemicals that digest food.
  • An obstruction. This is when something is stuck in the stomach or intestines.

To figure out what’s wrong with your dog or cat, your vet may need to:

  • Consider your pet's age, past illnesses, other animals it has been around, and other information about its health
  • Do a physical exam
  • Do lab tests on its blood or stool samples
  • Do X-rays or an ultrasound
  • Do a biopsy or other tests on samples of its fluids or tissues

After your vet figures out what’s wrong, your dog or cat may need:

  • Medicine that kills germs or parasites
  • Drugs to help with diarrhea or vomiting
  • Fluids to replace what it has lost because of diarrhea
  • Surgery
  • Pain medicine

Other Things That Cause Skin Problems

Itching and skin infections most often come from:

  • Fleas
  • Allergies to fleas
  • Allergies to things in the air or in the pet’s surroundings, like dust mites, pollen, or grasses

When fleas or a flea allergy are behind your pet’s skin condition, that’s usually the easiest thing to figure out. If you see fleas, your vet will fix you up with a product that kills them, and possibly also a medication to stop the allergic reaction to fleas. If the symptoms clear up, that’s it.

It’s harder to nail down if your dog or cat is allergic to things like pollen. Your vet will examine your pet, ask you about its health history, and do skin tests.

Once you know what your pet is allergic to, your vet can work out how to handle it. You may have to:

  • Keep your pet away from whatever it’s allergic to, if that’s possible.
  • Help your pet keep its coat clean.
  • See that your pet gets regular allergy shots or whatever medicine your vet prescribes.

Whatever the solution is, you’ll have to make a long-term commitment to stick with it. Your pet will depend on you.

Show Sources

SOURCES:

MSPCA Angell: “The Itchy Pet -- Food Allergies in Dogs and Cats.”

American Kennel Club: “How To Tell If Your Dog Has Food Allergies.”

American Kennel Club: “Types of Allergic Reactions in Dogs.”

American Kennel Club: “Dog Allergies: Symptoms and Treatment.”

Cornell University College of Veterinary Medicine: “Food Allergies.”

Cummings Veterinary Medical Center at Tufts University: “Your Dog,” “Catnip,” “What Every Pet Owner Should Know About Food Allergies.”

LSU School of Veterinary Medicine.

Australian Veterinary Journal.

VCA Hospitals: “Allergy -- Food Allergy in Dogs.”

Critical Reviews in Food Science and Nutrition: “Food allergy in dogs and cats: a review.”

Pet Food Institute: “Food Allergies.”

Banfield Pet Hospital: “Homemade Diets: Are They Right for Your Pet?”

Merck Veterinary Manual: “Allergies in Dogs,” “Overview of Food Allergy.”

DVM360: “Diagnosing food allergies in dogs and cats -- Bring your case to trial.”

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