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Food Allergies in Cats

This article is written by Pet Circle veterinarian, Dr Carla Paszkowski BVSc (Hons)

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.

Skip to a Section:

1. Most common causes of food allergies

2. Symptoms of Food Allergies

3. How is a Food Allergy diagnosed?

4. What is a Dietary Trial?

5. Hypoallergenic Diet Options for Cats

Further reading

Most Common Food Allergies in Cats

Fish, beef, and dairy products are observed to be the most common causes of food allergies in cats. Photo by Ronit HaNegby via Pexels.

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 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.

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 dietary trial.

Elimination Diet Trials

The three options for completing an elimination diet in cats.

To date, the only reliable method for the absolute diagnosis of food allergies is a dietary elimination trial.⁴ A 'dietary trial' or an 'elimination diet' is used as part of the diagnostic process to pinpoint which allergen your cat is allergic to.

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:

Ziwi Peak Air Dried Venison Recipe - this high-meat, limited ingredient diet is gently air-dried, grain-free, and contains no artificial flavours or preservatives. The recipe consists of 96% free-range venison, ethically raised on the green pastures of New Zealands South Island. It is not a single protein recipe as it also contains Green-Lipped Mussel (a seafood), however this is unlikely to cause reactions in cats. Also available in wet food.

Hills Prescription Diet D/D Skin & Food Sensitivities - specifically designed for food sensitivities, this prescription food is made with yellow & green peas and venison, which are great novel protein and carbohydrate sources. It also contains antioxidants, soybean & fish oil, and extra vitamins to help support the skin.

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.

The Best Diets for Food Allergies in Cats

If your veterinarian has recommended a prescription or veterinary hydrolysed diet, it's likely that they've recommended one of the following varieities. But what's the difference? Royal Canin Hypoallergenic versus Anallergenic? Hill's Z/d versus Hill's D/d? See the following table which highlights the characteristics of each: