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Cat Food Allergies

The problem

Something was giving Patches a rash. The 4-year-old calico had developed red bumps around her face and she scratched at her ears incessantly. Patches’ Pet Parents thought she was having an allergic reaction to an insect bite or some sort of plant she had rubbed up against. A trip to the vet revealed that the cause of the rash was indeed an allergy—a food allergy.

“Food allergies are the third most common cause of sensitive skin disorders after fleas or other external parasites and environmental triggers like pollen or grass,” according to Dr. Robyn Jaynes, PetSmart veterinary expert.

They are also difficult to detect because the symptoms mimic those of other disorders. Cat food allergies are often confused with pet food intolerance, when the food simply doesn’t agree with the pet.

Allergies, also referred to as food hypersensitivities, are adverse reactions of the immune system to a certain protein in the pet’s food like beef or dairy. Food intolerance is when a food simply doesn’t agree with your pet.

The symptoms

Common signs of food allergy in cats include severe itching especially around the head, neck and ears, scaling and in severe cases hair loss. Food allergies often develop in cats after eating the same type or brand of food for long periods of time.

The solution

“First consult your vet to determine if your pet has a food allergy or intolerance,” says Mark Finke, Ph.D. and a pet nutritionist. “Then try a premium food with a limited number of protein and carbohydrate sources.” Ask a PetSmart associate for recommendations on our best foods.

Your vet may also suggest a prescription food. To transition your pet to the new cat food, mix a small amount of the new food with the current food and increase the new food over the course of 10 days.


  • Avoid foods with the leading protein allergens for cats including beef, fish and dairy.
  • Avoid treats and people food.
  • Feed your pet the new diet for four to 12 weeks and document the type and amount of food your pet eats and any reactions they have. Review your notes with your vet, noting any changes in your pet’s symptoms.

Would an allergy test tell me what my pet is allergic to?

While allergy tests for dogs and cats are available, the accuracy of these tests is still undetermined. Simple elimination and trial and error with your pet’s diet is the best way to determine what is causing your pet’s reaction.

I’ve been feeding my pet the same food for years - can he still develop a food allergy?

According to studies conducted by veterinary dermatologists, dogs and cats can develop food allergies after eating one type or brand of food for a long period of time.

Can my pet be allergic or intolerant to certain additives in their pet food?

While food additives are often blamed for causing food allergies or food intolerance, there are no published cases of reactions caused by pet food additives.

The information used in this report is approved by PetSmart nutritionists and vet experts.

Information from “Small Animal Clinical Nutrition,” 4th Edition, Hand, Thatcher, Remillard, Roudebush, Copyright 2000 by Mark Morris Institute was used in this report.

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