Food Allergies in Cats: Symptoms, Causes, and Treatment

Food allergies are rare in cats—but they can cause several symptoms that involve both the digestive system and the skin. They’re the most common allergy in felines, just behind flea allergies and inhaled substances.  

Picking the right food for your cat’s allergy is an important decision that should be made in collaboration with your veterinarian.  

What Are Food Allergies in Cats?

A food allergy in cats is when a feline’s immune system overreacts to a food substance it has previously been exposed to.  

The immune system will create antibodies to a previously harmless protein, causing an inflammatory response in a cat’s body, which causes symptoms.   

For a cat to have a food allergy to a specific ingredient, they must have ingested that ingredient in the past. 

Cat food allergies most often affect the skin, causing:  

• Itching and scratching 

• Overgrooming 

• Secondary infections 

• Sores 

A food allergy in cats can also upset the gastrointestinal tract, causing diarrhea and/or vomiting. 

Food allergies are rare cats. It’s estimated that just 1% of all cats have food allergies, and up to 15% of itchy cats. Of cats with both itching and gastrointestinal symptoms, up to 42% could be food allergic. 

 While most cats with food allergies are over one year of age, studies have shown that cats of any age (or gender) can develop this issue. There is some evidence that Siamese cats and Siamese mix breeds are more prone to food allergies than other breeds. 

Cat Food Allergy Symptoms

The most common symptom of a food allergy in cats is constant itching that does not change or stop seasonally. Itching can occur anywhere on the body, but the head and neck are most often involved. 

Symptoms may also include: 

• Licking 

• Scratching 

• Overgrooming 

• Biting 

Skin lesions may also be present, which may include: 

• Small crusts (miliary dermatitis) 

• Redness 

• Papules 

• Self-induced trauma (sores due to biting, scratching, or licking) 

• Self-induced hair loss (due to biting, scratching, or licking) 

• Ulcerations 

• Plaques (raised circular nodules) 

Less commonly, there may be GI symptoms, including diarrhea and/or vomiting. 

What Causes Food Allergies in Cats?

A food allergy in cats can develop at any age, even if a feline has been eating the same food for a long period of time with no problems.  

Most known food allergies in cats are due to an abnormal reaction to proteins in food.  

Let’s look at are some common foods that cause allergies, but food allergies in cats can be caused by any food substance and are not limited these items. 

Food sources that most commonly cause food allergies in cats are: 

• Beef 

• Fish 

• Chicken 

Food sources that cause a food allergy in cats less commonly include: 

• Wheat 

• Corn 

• Dairy 

• Lamb 

• Egg 

• Barley 

• Rabbit 

How Veterinarians Diagnose Food Allergies in Cats

To diagnose a food allergy in cats, vets recommend feeding an affected cat a strict hypoallergenic diet for eight to 12 weeks to evaluate for improvement of symptoms. A hypoallergenic diet contains ingredients that are less likely to cause the immune system's inflammatory response against the body.  

This means that you only feed this specific diet.  

No additional treats, protein-flavored medications, or even certain formulations of medications (such as gelatin capsules) can be given. 

A hypoallergenic diet is started by choosing a novel protein which is a protein that your cat has never had before. Common diets include fish, duck, and venison. 

Alternatively, a hydrolyzed diet may be prescribed for the elimination food trial. Hydrolyzed food is a special veterinary diet that breaks down the proteins before a cat eats it.  

This prevents the immune system from recognizing the protein and thus reduces the chance of an allergic response. If improvement is seen, a hydrolyzed diet is continued indefinitely. Commercial diets such as these are formulated to be balanced for long-term feeding. 

There are many types of tests on the market to diagnose food allergies that involve collecting blood, hair, or saliva.  

However, none of these tests have been proven to be accurate in clinical studies. A hypoallergenic novel protein or hydrolyzed diet trial is the most common way to diagnose food allergies in cats.  

It’s important that you provide your vet with your cat’s complete diet history to help them with monitoring your cat’s response to a hypoallergenic food trial. The choice of food used during the trial will depend on this. 

If you use a novel protein diet, your vet will choose a protein source that your cat has never eaten before.  

Even with hydrolyzed protein diets, it’s preferable to choose one that is based on an ingredient to which your cat has not previously eaten. 

Some food-allergic cats who fail to respond to one diet may improve on another diet.

Treatment of Food Allergies in Cats

The treatment for a food allergy in cats is to provide a diet that does not contain any allergy-inducing ingredients.  

The specific food sources you may be able to feed your cat can vary greatly. Veterinary diets (which need a prescription by a veterinarian) are recommended when performing a hypoallergenic novel protein food trial because they have stricter quality control.  

Over-the-counter cat food can contain contaminants from other proteins which can still cause an allergic reaction (ex: a duck-based food might be made in the same machine as a chicken food and if the cat is allergic to chicken they will then react to a duck food). Over-the-counter diets can also have by products and other protein containing ingredients that would cause a food allergic cat to react.  

Most cats are very itchy when starting a hypoallergenic food trial, so symptomatic treatment may be necessary. It takes at least eight to 12 weeks for the old food to leave a cat’s system and the new food to take over.  

Low-dose corticosteroids, such as prednisolone, are often used for this purpose.  

Any secondary bacterial or yeast infections must also be treated with antibiotics (like Convenia) and/or antifungals (such as itraconazole), and repeated treatments may be necessary. 

Best Cat Food for Cats With Food Allergies

Prescription diets for cats with food allergies are divided into two main categories—novel proteins and hydrolyzed cat food.  

Always make sure to discuss any diet changes with your veterinarian to see if they’re the right choice to help alleviate your cat’s symptoms.   

Let’s look at a few diet options for cats with food allergies. 

Novel Protein Foods for Cats  

Hydrolyzed Foods for Cats