Itchy Dogs and Cats–A 3 Part Series: Part 2

Written by Dr. Angie Ahlstrom

Part 2: Food Allergies in Dogs and Cats

Recognizing food allergies in dogs and cats can be difficult. The symptoms can be varied and can be subtle in some cases. We will discuss the symptoms and treatment of food allergies in dogs and cats separately.

Dogs and cats are most often allergic to proteins in their food. Allergies to grains are exceedingly rare in pets; in fact, only Irish Setters have been found to have an allergy to rice. Food allergies are classified as an inflammatory reaction in the gastrointestinal (GI) tract to certain proteins. This inflammation leads to decreased absorption of nutrients in the GI tract and subsequent side effects in the skin and feces. Treatment of food allergies is aimed at decreasing the inflammation in the GI tract through a change in diet.

It is important to note that there is no blood test to diagnose food allergies. These allergies are diagnosed by a strict food trial. This means that your dog or cat should only be allowed to eat their new food—no human food or treats allowed. Diet trials take approximately 3 months to complete; remember, it takes years for the inflammation to build up in your pet’s GI tract and it will take time for the diet to decrease that inflammation.


Food allergies in dogs most frequently between 2-7 years of age.

Dogs are most commonly allergic to the following proteins:

  • Beef
  • Chicken and Turkey
  • Dairy

The following symptoms are most common in dogs with food allergies:

  • Itchy paws
  • Chronic and recurrent ear infections
  • Chronic anal gland problems—this includes anal gland impaction and infection
  • Intermittent chronic gastrointestinal signs including diarrhea and vomiting

There are 2 different methods of treating food allergies in dogs

  • Novel protein diet: These diets contain 1 protein source to which the dog has never been exposed. There are very few over the counter diets that meet this description. If you are going to try an over the counter diet, please read the ingredient label very carefully to make sure that there is only 1 protein source. Veterinary prescription diets are also available with a novel protein source; these diets are guaranteed to contain no other protein. Examples of new proteins that work well in dogs are salmon, rabbit, and duck. If your dog is feeling adventurous, there are also veterinary diets made with kangaroo!
  • Hydrolyzed protein diet: These diets contain proteins that have been broken in to smaller subunits. These subunits are so small that the body no longer recognizes them as allergens. These diets are only available from a veterinarian. If a novel protein diet fails to fully control food allergies in your dog, we would recommend transitioning to a hydrolyzed protein diet to eliminate any further reaction to full sized proteins.



Food allergies in cats generally occur in those older than 10 years. Food allergies generally go hand-in-hand with a condition called Inflammatory Bowel Disease (IBD) in cats. Studies have shown that IBD, left untreated, can lead to intestinal lymphoma. Therefore, cats can require more aggressive therapy to decrease the inflammation in their intestinal tracts and slow or stop the transition to lymphoma.

Cats are most commonly allergic to the following proteins:

  • Fish and Seafood
  • Chicken
  • Dairy

The following symptoms are most common in cats with food allergies:

  • Frequent vomiting—vomiting more frequently than every 3-4 weeks is not normal in cats
  • Weight loss—this is due to poor absorption of nutrients due to the inflammation in the GI tract
  • Loose stool—this is variably seen in cats with food allergies

Treatment options for cats with food allergies/Inflammatory Bowel Disease include the following:

  • Novel protein diets: similar to dogs, cats can benefit from a new protein source in their diet; this decreases inflammation over time as the body does not view the new protein as an allergen. Prescription diets and over the counter diets are available. If your cat has been definitively diagnosed with IBD (via intestinal biopsies), a veterinary diet generally provides more control over inflammation as there is no possibility for contamination of any other protein source.
  • Hydrolyzed protein diet: as with dogs, these diets are only available as a prescription from your veterinarian. They decrease the inflammation in the GI tract because the body does not recognized the small protein fragments as allergens.
  • Anti-inflammatory medications: prednisolone (a steroid) is used to more quickly control the inflammation in cats’ GI tracts. Long-term, diet change is the most important method to control food allergy and the chronic inflammation of IBD.

If you think your dog or cat could have a food allergy, schedule an appointment with your veterinarian to discuss your pets’ symptoms and decide the treatment option that it best for you.


Join us next week to learn about environmental allergies!



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