Grain Allergy in Cats

Grain Allergy in Cats - Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost

What is Grain Allergy?

An allergy to a food can develop at any age, and if left untreated, can cause significant health risks. Itchy skin can turn into skin wounds that can leave your cat vulnerable to bacterial infections. If digestive problems cause your cat to avoid his food, this can lead to weight loss that can compromise the health and wellbeing of your cat. Often, cats become sensitive to a food they have been eating for a long time, which causes many owners to overlook the fact that their cat may have an allergy to something in their diet.

Grain is a common filler in many dry cat foods, and is often added to protein and other starches to increase the volume of a food. However, grain is not a biologically appropriate food for cats, and over time, they can develop a sensitivity to grain that can cause gastrointestinal and skin problems. 

Symptoms of Grain Allergy in Cats

A food allergy often appears out of nowhere, as cats can develop a sensitivity to something that is constantly in their diet. Intermittent or chronic digestive complaints, skin problems, and even respiratory issues can appear gradually over many months or years. Skin rashes and wounds can appear on any area of the body, but are seen most commonly on the face, neck, belly, and legs. Signs can include:

  • Vomiting
  • Diarrhea
  • Loose stools
  • Loss of appetite
  • Weight loss
  • Itchy, reddened and inflamed skin
  • Excessive grooming
  • Excessive scratching
  • Rubbing face on objects
  • Skin lesions, scabs and rashes
  • Leathery patches of skin 
  • Lip ulcers
  • Miliary dermatitis, or little bumps and scabs commonly seen on the neck or rear areas
  • Bacterial skin infections
  • Hair loss
  • Ear infections 
  • Excessive ear wax
  • Cracked paw pads 
  • Scooting rear end on floor or carpets
  • Coughing
  • Seizures

Causes of Grain Allergy in Cats

In the wild, your cat’s diet would have consisted mainly of animal proteins. The only grains she might have eaten were trace amounts in the digestive tract of prey animals. Grain has never been a substantial part of the feline diet, but it has become a large part of commercial pet foods where it is used to bulk up the volume of those foods. 

An allergy to a food occurs when the immune system becomes sensitive to a particular food item. After repeated exposure to that food, the immune system sends large quantities of antibodies in the GI tract to target that food in an effort to remove it. This releases the chemical histamine, which causes the symptoms seen in an allergic reaction. 

Eating the same food every day can cause your cat to become sensitive to it. If like grain, it isn’t a food that your cat is biologically programmed to process, it can sit too long without being digested, which can trigger the immune response. Lumps on the skin and vomiting are the body’s way of trying to remove the foreign invader, for example grain.

Diagnosis of Grain Allergy in Cats

A diagnosis of a particular food allergy can be challenging, but there are methods to determine what is causing the symptoms in your cat. A food allergy test can be performed, either with a blood test or a skin test. The blood test can measure the IgE antibody count and type that is present in the bloodstream, while the skin test injects various allergens into the skin to see which one causes a reaction. These allergy tests are not completely accurate, and they are often performed when other methods have failed to produce a diagnosis.

The main diagnostic method for a possible food allergy is to change your cat’s diet. There are many types of diets available, but your veterinarian will recommend one that contains ingredients not already in your cat’s current diet. This can be a protein change, such as changing from chicken or fish to rabbit or duck. It could also be a grain, corn, or soy free diet, a homemade or raw diet, or even a hydrolyzed diet, which breaks down the proteins into smaller pieces that are unrecognizable by the immune system.

The specialized diet needs to be fed for 4 to 12 weeks, without any treats or other foods given that are not made with the same ingredients. Often, to confirm the findings from the results of this diet change, the old food may be reintroduced afterwards to see if the same reaction occurs. This method can help to make a diagnosis of a grain allergy.

In some cases, your veterinarian may take skin or intestinal biopsies for further testing to confirm that an allergy is the problem, although it cannot help to determine what your cat is allergic to.

Treatment of Grain Allergy in Cats

The treatment of a grain allergy is to eliminate grain from your cat’s diet. This can be accomplished with a change of cat food to a grain-free dry, canned, raw, or homemade food. 

Once your cat is eating a grain-free diet for 8 to 10 weeks, symptoms should disappear as your cat’s immune system is relaxing and the body has been detoxified. Your veterinarian may recommend supplements to aid the immune system and help with the detoxification process. Antibiotics may be prescribed to treat any secondary infections. Anti-inflammatories and a safe ear cleaning solution can be used to treat ear infections. Itchy skin can be calmed with medicated shampoo baths. Corticosteroids may also be prescribed for a short time to aid in reducing skin inflammation.

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Recovery of Grain Allergy in Cats

A food allergy to grain is not curable, but keeping grain out of your cat’s diet will ensure that she will not suffer from any symptoms of an allergic response. Generally, after 2 to 3 months of a grain-free diet, symptoms should disappear, leaving your cat healthy and happy. If grain is fed to your cat again, you may see those symptoms reappear within a week or two. 

While it is impossible to predict when a food allergy may develop, many experts suggest providing a rotating variety of foods for your cat that is appropriate to her needs. This can provide a balanced nutritional base while reducing the risk of developing a sensitivity.

Grain Allergy Questions and Advice from Veterinary Professionals


Domestic shorthair



Six Months


3 found this helpful


3 found this helpful

My pet has the following symptoms:
Upset Stomach, Hunching, Vomiting
At what age does food intolerance show up in cats? Kittens food is grain free been on it for two months. 14 year old other cat just changed food, not grain free, and kitten has been experiencing these symptoms since getting into the food. Foods are the same brand, just different formulas.

Sept. 29, 2020

Answered by Dr. Michele K. DVM

3 Recommendations

Thank you for your question. Food intolerance can show up at any point, as there are some ingredients in some foods that just do not sit well with the intestines. If your kitten has started showing signs like that after switching Foods, it makes sense to me to try a different food. The signs you are describing can also be due to parasites or other causes, so if things do not improve, it would probably be best to have her seen by a veterinarian. I hope that all goes well for both cats.

Oct. 1, 2020

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American Short Hair




5 Years


2 found this helpful


2 found this helpful

My pet has the following symptoms:
Diarrhea Vomiting Loss Of Apatite
My cat Karma has been on a grain free diet for while now since i found out about her allergy a few years back. But i had to improvise one morning and had to give her some wet food not grain free. Its been almost a week since then and she has terrible diarrhea and just today has been puking a lot. Im just wondering if this is because she ate food with grain or if I should be more concerned?

July 17, 2018

2 Recommendations

Any sudden dietary change with or without an allergen may lead to diarrhoea, vomiting and abdominal pain; it is likely that the sudden change is having an effect more than anything else. Move back over the the regular diet and monitor for improvement, if there are no signs of improvement visit your Veterinarian. Regards Dr Callum Turner DVM

July 17, 2018

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