Dry Food Allergy in Cats

Your cat’s immune system functions the same way it does in people.  The main purpose of the immune system is to protect the body from bacteria, viruses and other “invaders” which can cause diseases.  What occurs in food allergies is the immune system’s line of defense overreacts and attacks the allergen “invader”. An allergen is the food item that causes the allergic reaction.

Most commercial dry cat foods are highly processed and are full of artificial ingredients, hormones, flavor enhancers, fillers, preservatives and dyes. Cats are carnivores and are not meant to eat large amounts of carbohydrates. Cats also do not tend to drink a lot of water; in the wild cats get water from eating their prey (50-70% water).   The average cat dry food has 25-50% carbohydrates.  The other concerns with dry food are they lack moisture (less than 10% water) and they do not have the adequate amount of protein.  Some dry food actually derives their protein from plants and not a meat source. Cats are not vegetarians and should not be fed as such.  Terms on a package label such as meat meal, chicken meal, and meat by product are too vague. The first ingredient on the package label should be an identified meat (beef, lamb, chicken or salmon).

Food allergies are the third most common type of allergies in cats.  If your cat is showing signs of food allergies, he should be seen by a veterinarian as soon as possible.

A food allergy occurs when a cat’s immune system reacts to a food item as if it were a threat to the body.  The immune system then creates an antibody (IgE) to fight the intruder. When the food item is ingested, it triggers the immune system to produce histamine and other chemicals, which cause allergy symptoms in the cat.

Symptoms may include:

• Red bumps and lesion
• Patches of hair loss
• Excessive itching
• Biting at skin
• Skin ulceration
• Neck dermatitis
• Crusty skin
• Behavioral changes
• Chronic ear infections
• Recurring skin bacterial infections or yeast infections

Common allergens in cat food allergies are:

• Corn - Corn meal and corn gluten are used as fillers in commercial dry food
• Rice - Brewers rice is used as a filler
• Dairy products - Such as milk powder or cheese
• Eggs - Sometimes added to food for a protein source
• Meat by product - Unknown, non-rendered ingredients; may contain organs, pieces of tail, hooves, fatty tissue, intestines, blood, or bone; these by products provide less nutrition
• Preservatives - Such as BHA or BHT; additionally, these preservatives may be carcinogens
• Soy products - Plant derived protein
• Wheat gluten - Used as a filler
• Beef, lamb, chicken, pork or fish

The physical examination of your cat by the veterinarian may be strongly indicative of a food allergy. Irritation of the skin may point to a reaction to the food; hair loss, itching, evidence of self biting and lesions will all present as an allergy. The veterinarian will need to investigate other possible causes however, such as parasitic infestation or contact toxicity. A skin scraping may be suggested for evaluation under the microscope. Your cat’s ears will be closely examined for infection

A discussion of your pet’s environment, dietary habits, exposure to the outdoors and possibility of contact with hazardous household products or noxious plants will be part of the diagnostic process. The symptoms leading up to the visit are important to relay as well. Let your veterinarian know the details of your feline’s recent behavior and if there is a history of vomiting or diarrhea; it is essential to relay the details to the vet and will help to narrow the diagnosis.

The short term treatment for food allergies may include antihistamines and corticosteroids.  Patients with skin infection or otitis may be prescribed antibiotics.  Topical antibiotics may also be recommended.  The cat may need to wear a cone to prevent him from licking or biting at his skin.  

The long term treatment of food allergy is to identify the allergen.  Research has proven that serology testing and/or skin testing are not accurate in identifying the allergen causing the allergic reaction. The most common way to identify the allergen is by an elimination diet. A protein and a carbohydrate are fed to the cat for 8-12 weeks, such as duck and sweet potato.  At the end of the 8-12 weeks a new protein and carbohydrate are introduced (perhaps chicken and potato). The veterinarian may recommend adding only one new item at a time. The food trial should continue for a few months.  If the cat shows a reaction to one of the ingredients it should be discontinued from his diet.  It is a good idea to write down the foods you are feeding your cat and any reactions in a log. 

During this time the cat should not be fed treats or flavored vitamins.  All members of the household must be asked to comply with the trial .A homemade diet is the better route but there are commercial diets the veterinarian may recommend.  A homemade diet is not as difficult as you may think.  The use of a crock pot can be a convenient way to easily prepare meals for your cat.  Unused portions can be refrigerated or frozen for future use.

Once the allergen is identified it should not be fed again.  Cats that are treated for food allergies have a good prognosis.  The patient will need follow up visits to monitor his progress and to re-examine his skin.  If the cat had a bacterial infection, a complete blood count (CBC) will need to be retaken.  Occasionally cats can develop new food allergies; the process of an elimination diet will need to be redone.