Food Allergies in Dogs
Reviewed for accuracy on March 19, 2020 by Sarah Wallace, DVM
With all the mysterious ingredients in pet foods nowadays, allergic reactions and intolerances are very common. Intolerances to food are different than food allergies; with intolerance the ingredient may not agree with the animal’s digestive system, but doesn’t invoke an immune response. Additives like wheat, corn, coloring, and dairy products aren’t what you’d normally consider to be dog food, but often they’re added in your pet’s food. While the symptoms can be similar, here’s how the two conditions are very different.
Just like environmental allergies, food allergies are caused by antibodies in the dog’s intestines overreacting to a particular allergen, leading to a histamine response – this reaction is what causes the visible symptoms. The allergic reaction is caused by a protein source in the food. It is possible for dogs to be allergic to the protein part of lactose, wheat, and soy just like humans. Food allergies and intolerances aren’t influenced by gender, breed, size, or even age; dogs can develop them at any point in their lives.
A particular ingredient in their food causes the immune reaction. The following are the most common problem foods, in order:
- Chicken eggs
- Fish (cats)
These ingredients are the most commonly found ingredients in pet foods, and therefore pets have been continuously exposed repeatedly throughout their lives.
Much less commonly, dogs can develop a food allergy to vegetables and carbohydrates as well – these ingredients have less protein than animal meat, and that makes them less likely to cause an allergic reaction. Grain allergies are rare, gluten allergies are even rarer – only having been documented in Irish Setters, possibly in Border Terriers and has never been seen in cats.
Allergies and intolerances have many of the same symptoms, but very different internal responses.
- Weight loss
- Abdominal pain
- Excessive flatulence
- Anorexia (lack of appetite) due to food intolerance occurs because of the inability to digest the food
Caused by the immune system, allergic reactions cause:
- Low appetite
- Excessive flatulence
- Itchy skin
Skin conditions are a large part of food allergies; histamines can make your pet’s skin miserably itchy to live in. Dogs will scratch, bite, rub and roll to try to satisfy the itch. Dogs can itch themselves to the point of wounds, or sores and can develop secondary skin infections from bacteria and yeast.
If your pet is scratching themselves more than a couple times per day or showing any of the other signs of food allergy or intolerance, you should bring them to your veterinarian right away to figure out the cause and how to make them more comfortable.
Diagnosis and Treatment
A physical exam will be performed by the vet, as well as blood and urine tests to rule out any underlying diseases. A thorough history of the symptoms and any changes in your dog’s diet will also be needed in order to diagnose your pet. Dogs with extreme vomiting and diarrhea may need hospitalization to replenish fluids, and antibiotics may be given if your pet has open wounds with the potential for infection.
A food elimination diet, also called a “diet trial”, for 8-12 weeks is the only effective way to diagnose food allergies and intolerances. Your vet will choose a novel food that your dog has not had access to before. It’s extremely important to stick to only this food – no treats or table scraps – otherwise you are wasting your time. The purpose of the elimination diet is to see if your pet improves when they are not eating their previous food.
Saliva or blood food allergy tests are unreliable and are not accurate ways to assess food allergies or intolerances. Save your money and put it towards the diet trial food.
Managing Food Allergies
If the elimination diet was successful, stick to a veterinarian-recommended food that doesn’t contain the trigger. Make sure you carefully read the ingredients on treats, vitamins, chewable toys, and medications, checking that they are free from the allergenic food. Inform all family members of the new diet to ensure there are no slip-ups. Don’t feed your dog table scraps or human snacks just in case.
Food allergies and intolerances are very common among dogs; they account for roughly 20% of all excessive scratching! See a veterinarian if your dog’s itching becomes so severe that it causes bleeding, rawness, or baldness. Any diarrhea or vomiting warrants a veterinary appointment as well, as these can be symptoms of other diseases. If your veterinarian recommends a specific diet, it’s extremely important to stick to it; allergies are often progressive, and symptoms can worsen with each feeding of the allergen.
Want to know more about conditions that can affect your dog? Check out the Healthy Paws Cost of Pet Health Care report for 2017.