Last Updated: 31/07/2025

Food Allergies in Cats: Symptoms, Diagnosis and Treatment

Suspect a food allergy in your cat? Before you change their diet, rule out fleas - the #1 cause of itching! Our vet guide then walks you through diagnosing a true food allergy, identifying triggers like beef or fish, and finding the right hypoallergenic or novel protein diet for lasting relief.

Author: Dr Carla Paszkowski BVSc (Hons)

Reading Time: 5 minutes - short read

A food allergy is an adverse reaction by the immune system to a specific protein found in food. Studies have shown that food allergies are the third most common type of allergy in cats, ranked only behind allergies to flea bites and inhaled substances. 1 That said, true food allergies are quite rare (found in only 1% of cats)2 while food intollerences - another type of adverse reaction that does not involve the immune system - are much more common.

Most Common Food Allergies in Cats

Due to the biochemistry of an allergic reaction, the cause of food allergies is usually the protein in the food - for example fish, beef, dairy or chicken.3 These proteins usually resist the heat of cooking, stomach acids, and intestinal digestive enzymes, and make their way to the bloodstream and target organs where they can cause an allergic reaction.

Most common foods that cause allergies in cats:

Fish
Beef
Dairy

Less common foods that cause allergies in cats:

Egg
Chicken
Wheat
Corn
Pork

Most cats that develop food allergies do so over a period of months or years of being exposed to a particular food. Damage to the intestinal tract can also lead to allergies and intollerences - this is sometimes seen with inflammatory diseases, infection, surgery and some medications. Some kittens who suffer from a gastrointestinal parasite or bacterial infection may develop food sensitivities, possibly because of early treatment with antibiotics.

Symptoms of a Food Allergy

Most commonly, feline food allergies present on the skin. Itchy, irritated and dry skin occurs particularly around the face, head and neck. An estimated 10-15% of food allergic cats also show gastrointestinal signs, such as vomiting and diarrhea.

Cats with adverse food reactions will display these signs all year round, unlike other causes of itchy skin such as environmental allergies which may flare up during spring. While cats of any age can develop adverse food reactions, it's more common in kittens and young adults with signs usually appearing before 3 years of age.

Symptoms of food allergies in cats include:

Pruritus - severe itching of the skin. The itching can affect any part of the body, but typically is worst on the face, head and neck.
Pustules - small, pale, fluid-filled lumps on the cat's skin
Hair loss - this is mostly a secondary symptom due to excessive scratching over time
Ear infections - a common secondary consequence of inflamed skin.
Vomiting, diarrhoea, and gas - Approximately 10-15% of cats have concurrent gastrointestinal signs such as vomiting, diarrhoea, flatulence and colitis

For more info on itchy skin management, check out our article The Causes of Itching in Cats.

How are Food Allergies Diagnosed?

If your cat has itchy skin, it can be difficult to determine the underlying cause. However, flea allergy dermatitis is undisputedly the most common cause of itchiness in cats, so it's essential to rule this out first. Vets have a common saying - 'itchy cats have fleas until proven otherwise'. Therefore, the first thing to do is ensure your cat's flea prevention is up to date with a reliable product like Bravecto, Revolution Plus, or Seresto. Never use a flea shampoo - not only can these be toxic to cats but they simply don't work on resilient Australian fleas!

Read more about how to truly get rid of fleas in our article How to Get Rid of Fleas on Your Cat.

If you've treated your cat for fleas and they are still itchy, your best bet is to consult your veterinarian for further advice. They will be able to rule out other conditions (such as ringworm, bacterial infections, or mites) and may then recommend a Elimination Diet Trial.

Elimination Diet Trials

The 3 Options For A Dietary Trial

A novel ("new") protein diet
A hydrolysed diet - these are prescription/veterinary diets which can only be recommended by your veterinarian
Home-cooked diet

The chosen diet must be fed exclusively for a minimum of 6 weeks, with absolutely no treats or tidbits as this may affect results. All other flavoured tablets (e.g. heartworm prophylaxis), flavoured antibiotics and vitamins, toothpastes, pigs ears and rawhides must be excluded. (Every family member should be aware of how important this is!). If the symptoms improve after 4-6 weeks on the dietary trial, a food reaction was likely responsible for your pet's symptoms. You can then introduce one ingredient per week (for example, try chicken the first week, then beef the next week, etc) and observe for a reaction. This allows you to pinpoint which ingredient your pet is allergic to.

The different types of diets that can be used for an elimination trial are outlined below:

1. A Novel Protein Diet

What is it? A diet containing a new protein source that your pet is unlikely to have eaten before, such as venison, rabbit, goat, or kangaroo. The ideal diet is also single protein (ie, doesn't contain multiple meats).

Pros: Commercially available, highly palatable, easy to use, affordable

Cons: Choices have become more limited due to expansion of pet food industry; protein sources that were once "unusual" are now more common

Top Novel Protein Diets for Cats

2. A Hydrolysed Diet

What is it? A diet in which the protein source is broken down via a 'hydrolysis' process into smaller molecules that are unlikely to trigger an allergic response.

Pros Commercially available - however must be prescribed by a veterinarian. Gold standard for elimination trials - generally considered 'allergy-proof' as the immune system cannot bind to hydrolysed proteins to create a reaction.

Cons: More expensive, reduced palatability, and a lack of evidence documenting whether cats allergic to the parent protein will actually tolerate a hydrolysed product.

Top Hydrolysed Diets for Cats:

Hill's Prescription Diet Z/d - made with hydrolysed poultry, clinical nutrition specially formulated to help avoid adverse food reactions in cats.

Royal Canin Hypoallergenic - made with hydrolysed soy protein, it is also formulated with a patented skin barrier complex to strengthen the skin's natural barrier function.

Royal Canin Anallergenic - made with hydrolysed chicken feathers. Due to the very small size of the protein and its novel origin it is extremely unlikely to trigger a food allergy.

3. Home-Cooked Diet

What Is it? A diet prepared at home with a novel protein and carbohydrate source.

Pros: Can be prepared affordably depending on the recipe.

Cons: Contraindicated in growing animals due to risk of skeletal and organ pathology if incorrectly formulated or balanced, not ideal in cats, not recommended for long-term feeding

Top home cooked diet ideas: Usually a good home cooked diet consists of 1 protein and 1 carbohydrate source e.g. Kangaroo and potatoes. As taurine deficiency is a particular risk in cats, we recommend consulting with a veterinary nutritionist in order to create a balanced recipe.

Pinpointing a food allergy in your cat is a clear and methodical process. The journey begins not with food, but with ruling out the most common cause of itchy skin: fleas. Ensure your cat is on a reliable, vet-recommended flea preventative first.

If the itching persists, a strict elimination diet trial, conducted under the guidance of your veterinarian, is the only reliable way to identify the specific protein causing the reaction. This process requires patience, but it is the key to finding a long-term diet that will keep your feline friend comfortable, happy, and symptom-free.

History

Our experts continually monitor the health and wellness space and we update our articles when new information becomes available.

Feb 14 2023

Written by Dr Carla Paszkowski BVSc (Hons)

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About the Author

Dr Carla Paszkowski BVSc (Hons)

Veterinarian

Dr. Carla graduated from the University of Queensland in 2013 with a Bachelor of Veterinary Science and worked for a number of years in small animal clinics across South East Queensland. While Carla enjoys most facets of clinical veterinary work, she holds a special passion for feline medicine, pocket pets, and nutrition.