What are food allergies or intolerances?
Food allergies are the result of over-sensitivity of the immune system to certain ingredients in food. Food allergies are more severe than food intolerances.
If your cat has a food intolerance, the problem is not immunological and may be caused by eating a spoiled food or attributed to an underlying disease, or it is possible that your cat doesn't have the enzymes necessary to digest her food.
When your cat eats something that she has an allergic reaction to, her body releases histamines which can cause itchy skin, general redness of the skin, or digestive problems like vomiting and diarrhoea.
The only way to identify a food allergy in your cat is to use an elimination food. An elimination food contains ingredients which are far less likely to cause an allergic reaction and hence helps you find out if the allergy is caused by elements in your cat’s regular food. Your vet will recommend your cat eat an allergen-free food for a fixed period. It's importantt you follow your vet's instructions precisely as feeding other foods may lead to poor results.
How to manage food allergy in cats
Hydrolysed peptides are too small to link receptors, hence they do not trigger release of histamine and cause allergic signs.
Food allergies are almost always triggered by proteins in food. When your cat eats a protein that she is allergic to, the protein molecule connects two sensitised receptor molecules in the body, which releases histamine.
There are two main ways to manage food allergies.
Hydrolysation reduces protein molecules to a size that doesn’t cause a reaction but leaves their nutritional value intact. The level of hydrolysation is measured in units called daltons, and the lower the number the better. The protein molecules in ordinary cat food are around 12,000 daltons in size. Proteins as small as 4,500 daltons have been known to cause allergic reactions. The major part of the protein in Hill’s™ Prescription Diet™ z/d™ ULTRA, a highly hydrolysed nutrition, is smaller than 3,000 daltons.
A novel protein is one that your cat has probably not eaten before. The receptor molecules in her body are therefore not sensitised to it, so it is unlikely to cause an allergic reaction. Hill’s Prescription Diet d/d™, for example, uses venison as a protein source.