Food allergies develop over extended periods of time, sometimes as long as months or years. Exposure to certain foods may cause the immune system to build a defense against a specific protein or carbohydrate molecule over time. The skin irritation caused by most food allergies may prompt a cat to harm itself from over-scratching. This can leave the cat vulnerable to secondary bacterial infections of the skin. Veterinary attention is needed to help identify the allergen and eliminate the corresponding symptoms.

Food allergies or intolerances happen when the immune system overreacts to a certain food item after it has been eaten. Antibodies respond to the food item, which often leads to “leaky gut syndrome,” and produces symptoms such as skin irritations or gastrointestinal issues. Food allergies make up the third most commonly occurring allergies in cats. 

One major indication that a food allergy is present is the continuation of symptoms year-round. Certain symptoms can prove threatening to the cat’s overall health and should be addressed promptly. Symptoms are as follows:

The exact reason a food that has been consumed for some time can develop into an allergen is unknown. There seems to be no link between breed, age, or sex of a cat and the occurrence of food allergies. More often than not, a low-quality protein source may be found as the allergen. Possible causes include:

To determine what allergen is causing symptoms in your cat, the veterinarian will need to perform a physical examination. You will be asked about the cat’s diet, including how long it has been given its typical food. The vet will have to differentiate between food allergies and other common allergies in cats, such as insect bites. Mange and infection will have to be ruled out or treated if also present.

The best way to diagnose a food allergy is to implement a “novel diet”, which uses the process of elimination to identify the allergen. The cat will be switched to a strict diet of two foods (one protein and one carbohydrate) that it has never eaten in its lifetime. For eight to ten weeks, the cat will remain on this simple diet until all previously seen symptoms have vanished. At that point, one new food item may be introduced. If no symptoms occur in the following two weeks, it is safe to assume that food is not the allergen. If symptoms do arise, the allergen has been identified. Additional food items may added in this fashion. This is a lengthy process that requires patience to be successful.

Once the allergen has been identified, it must be permanently excluded from the cat’s diet. Abstaining from that food is the only long-term solution to stop symptoms from coming back. 

Your veterinary nutritionist may develop a specific diet tailored to your cat’s needs. Generally, a diet that is low in carbohydrates and high in good quality protein is preferred. This diet may have two to three protein sources that do not irritate the cat. You will need to rotate the protein type every three to six months to help prevent more food allergies forming in the cat. The diet may be commercially prepared or it may have to be homemade.

To provide relief of symptoms immediately, antihistamines may be administered. This is only a short term solution, but may be necessary if the cat is suffering. 

If a secondary bacterial infection is present in the skin, an antibiotic may be prescribed to rid the body of the harmful bacteria. Prescriptions generally range from two to four weeks.

Once the new diet is started, probiotics can be helpful in aiding food digestion. They can restore the good bacteria that the gastrointestinal tract needs to function properly.

If food allergy symptoms do not disappear in the eight to ten weeks after diet introduction, see your vet to ensure diagnosis is correct. Once a cat is allergic to a food item, the allergy will almost always remain unless the gastrointestinal tract detoxifies and heals. If the novel diet seems to be working for your cat, stop introducing foods after you have found two or three protein sources that do not cause symptoms. If new food allergies start to develop, a diet change may be needed again.

To prevent food allergies from occurring in the first place, try to feed your cat a species-appropriate diet. Avoid low-quality protein sources such as hooves or beaks. Grain fillers can also be excluded as they do not nutritionally contribute to a cat. Work with a cat nutrition specialist when forming a standard diet for any cat.