By Jean Hofve, DVM
Cats often develop “food allergies” or “food intolerances” to ingredients found in commercial cat food. The top allergens are: chicken, fish and corn (very common cat food ingredients), beef (often referred to as “meat by-products” or “meat and bone meal” on pet food labels), wheat, and dairy products. However, an allergy can develop to any protein to which the cat is repeatedly or constantly exposed.
The symptoms of food allergy are typically either skin-related or digestion-related.
- Skin symptoms include rashes (particularly around the face and ears), excessive licking (typically paws, legs or tummy), and red, itchy ears.
- Digestive symptoms include vomiting and diarrhea. These are similar to the symptoms of inflammatory bowel disease.
Food allergies are often confused with atopy, or inhalant allergies. Both can cause skin symptoms. Here’s a quick 2-minute video explanation:
The conventional treatments for food allergies are steroids (also called “corticosteroids” and “glucocorticoids” to distinguish them from the anabolic steroids that bodybuilders and athletes sometimes use), hyposensitization, and diet therapy.
Steroids can be given by long-lasting injection (“Depo-Medrol” or other injectable cortisone) or by mouth in the form of a tablet. The two most common oral steroids are prednisone and prednisolone. Prednisone is hard for cats to metabolize and must be converted to prednisolone in the liver before it will work. Therefore, it is simpler and less stressful to give prednisolone itself.
However, steroids have many dangerous side effects. The injectable forms can cause diabetes. Steroids can also damage the kidneys. The primary action of steroids is to suppress the immune system, so that the inflammatory reaction to the allergen does not occur. This makes the cat more prone to infections. Steroids can also cause ulcers in the stomach and intestines. Cats receiving steroids should not be vaccinated because the steroid prevents the immune system from responding to the vaccine.
Hyposensitization is not often used in cats, and requires knowing precisely what the cat is allergic to. Once this is determined, then the substance is diluted and injected to signal to the immune system that the substance is not harmful and it doesn’t need to over-react. The skin test is considered the “gold standard”; there is also a blood test for allergies (sometimes called a “Rast” test). While both work well in dogs, they are notoriously inaccurate in cats.
Diet trials use “novel” ingredients that are not commonly found in pet food. Novel protein sources include kangaroo, emu, venison, rabbit, and duck. Novel carbohydrate sources include green peas, potatoes, and barley. Lamb and rice used to be novel, but since the introduction of lamb and rice foods years ago, many animals have (predictably) become allergic to those, too. The prescription-type diets (using green peas and novel meat sources) are available from some veterinarians., and there are a few OTC choices as well. Be sure to read the ingredient list! A diet trial must last at least 8 weeks (preferably 12) and must include only the test food; no treats, no exceptions. Just one diet slip (such as giving a treat containing chicken) could invalidate the entire trial and you will have to start over.
Holistic treatments for food allergies include homemade diets using novel ingredients, natural anti-inflammatories like slippery elm and antioxidants, skin-healing supplements like Omega-3 fatty acids, and other immune-supporting treatments like BioSuperfood.
It should also be noted that even in cats who are not specifically allergic to something in the food still often do better with a hypoallergenic diet. It seems that the fewer allergens the immune system has to deal with, the less chance it will over-react to any of them.