Pets can develop “food allergies” or “food intolerances” to ingredients found in commercial cat food. What’s the difference? Food intolerance, which is much more common, is an adverse reaction to something in the food, such as dyes, preservatives, texturizers, or other additives. Food intolerances typically produce digestive symptoms, such as vomiting and diarrhea. A true food allergy is due to an immune system reaction called “hypersensitivity.” In particular, it is a Type I “immediate” hypersensitivity reaction in which the immune system makes antibodies to the allergen (allergy-causing substance).
The symptoms of food allergy are typically either skin-related, although occasionally digestive symptoms are seen.
- Skin symptoms include rashes (particularly around the face and ears), excessive licking (typically paws, legs or tummy), and inflamed, itchy ears. Secondary yeast and bacterial infections are common and must also be treated.
- Digestive symptoms include vomiting and diarrhea. These are similar to the symptoms of inflammatory bowel disease, which may itself be triggered by a food allergy.
Cats are more likely to develop true allergies to foods than are dogs. Only about 10% of dogs with skin and ear symptoms are food-allergic, but food allergies may account for as many as 50% of cats with the same symptoms.
The top allergens in pets are: beef (often referred to as “meat by-products” or “meat and bone meal” on pet food labels), dairy products, chicken (may be labeled as “poultry”), fish, wheat, eggs, corn, and soy. These allergens are, not coincidentally, the most common ingredients in pet foods.
An allergy can develop to any protein to which the pet is repeatedly or constantly exposed. Feeding the same food for years on end is the best way to create a food allergy. This is why we recommend varying the brands and flavors you feed your pet.
The first step in any suspected food intolerance or allergy is a “hypoallergenic” diet trial. These 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. OTC choices include Nature’s Variety Prairie (lamb, duck, rabbit and venison), EVO 95% meat varieties, and Merrick Thanksgiving Day Dinner (turkey).
A diet trial lasts 8-12 weeks (it takes a long time to resolve skin symptoms) 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, make your pet miserable, and force you to start the entire trial over from the beginning.
The main drug treatment for food allergy is 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.
The primary action of steroids is to suppress the immune system, so that the inflammatory reaction to the allergen does not occur. However, steroids have many dangerous side effects, including diabetes and ulceration in the digestive tract. Dogs are much more sensitive to the effects of steroids than cats; steriods should be used with extreme caution in all pets. Pets receiving steroids should not be vaccinated because the steroid prevents the immune system from responding to the vaccine.
Hyposensitization is another potential treatment, but is used more in dogs than cats. It requires knowing precisely what the pet is allergic to. This is best accomplished with a skin test done under anesthesia. The skin test is considered the “gold standard”; but there is also a blood test for allergies (sometimes called a “Rast” test). While both work well in dogs, they are not accurate for cats. Once the allergens are determined, each substance is diluted; they are then mixed together and injected. The tiny amount used tells the immune system that the substances are not harmful and it doesn’t need to over-react.
Holistic treatments for food allergies include:
1. Homemade, or raw diets using fresh, whole food ingredients. Even though a dog or cat is allergic to a protein in commercial pet food, that same protein, fed fresh, may not be problematic. That’s because heat-processing of canned and dry foods can alter the natural proteins, creating abnormal shapes that trigger an immune reaction. If possible, when starting out, it’s best to use a novel protein source to allow time for the immune system to calm down and the gut to heal. Once symptoms resolve, you can re-introduce other ingredients one by one to test for reaction. If using a commercially prepared food (including raw or dehydrated diets and all supplements), always read the ingredients. Some products claim to be low-allergen but still contain chicken, fish, or other likely allergy suspects.
2. Natural anti-inflammatories. Antioxidants and Omega-3 fatty acids have good anti-inflammatory action; Omega-3s are also beneficial for skin healing. Fish and cod liver oils are the best source of Omega 3s for pets, and high-quality distilled oils should not contain any fish proteins; but if your pet is allergic to fish and reacts to a fish oil product, you may want to substitute flaxseed oil. Always read the label to make sure that there are no potential allergens used as a flavoring or base. Safe, excellent-quality products include:
Pure Essentials for Mature Dogs
Genesis Resources Feline Antioxidant Formula
Nordic Naturals Omega-3 Pet and Cod Liver Oil
3. Digestive support: Enzymes and Probiotics
Giving digestive enzymes with food helps the gut break particles down and reduces the chance that allergenic proteins will remain intact long enough to provoke an immune response. Probiotics help protect the intestinal tract and promote a healthy bacterial population, which may reduce inflammation. Here are some convenient, safe products:
Pet Naturals Digestive Support for Dogs and Cats (contains enzymes and probiotics)
Animal Essentials Plant Enzymes and Probiotics
It should also be noted that even in pets who are not specifically allergic to something in the food (such as dogs with atopy, or cats with asthma) 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.