True Allergies
True allergic responses are reactions to toxic irritations in the body. They trigger histamine reactions which are always similar, whether your cat breathes in the allergen or eats it or absorbs it through the skin. Extreme allergic reactions can cause shock and even death in cats. This is rare, but it happens.
A Cat's Allergic Reaction to Cat Food
Food allergies are true allergies. This means the allergy symptoms will include itching, rashes or lesions and inflammations causing swelling or nasal and respiratory congestion. These are the very symptoms we see with other problems like skin allergies.
The substance causing irritation in this case is cat food. Food allergies often trouble cats prone to allergic reactions to other things in the environment, or to newly prescribed medications, so it is often difficult to pin down what is causing a reaction in any given case. There are situations where a strong clue that a cat food allergy is at the bottom of things will present itself. For instance; if your cat is scratching or showing several allergic symptoms through the winter or all year round, you should begin to suspect a cat food allergy. If the symptoms do not seem to respond to steroid treatment then cat food allergies may be involved.
A Cat's Food Intolerance
Intolerance is a very different problem associated primarily with digestion. Intolerance happens when your cat's body simply cannot process the food for some reason. The symptoms arising from this disorder will be entirely different. Intolerances produce vomiting, diarrhea and related digestive difficulties.
Remember that whether it is intolerance or allergy, the problem may not go away just because you change the brand of food you feed your cat. The reaction maybe to a particular ingredient found in 10 or 20 brands of cat food. You may find the problem persists after you switch to a homemade recipe.
Treatment for Allergies and Intolerance
Short term: the symptoms in both situations will respond to medication. For the long term, your vet can help you treat both allergy and intolerance to cat foods by the straight forward method of eliminating the food or ingredient causing the difficulty. Your vet will guide you through two procedures; one called Food Trials and another called an Elimination Diet. You may have to follow strict feeding procedures using specific formulas over a number of weeks, but eventually you will isolate the ingredient causing the difficulty and eliminate it from your cat's diet.