One of the most common conditions affecting cats at the Animal Clinic at Thorndale is allergy. In the allergic state, a cat’s immune system “overreacts” to foreign substances (allergens or antigens) to which it is exposed. These overreactions are manifested in three ways. The most common is itching of the skin, either localized (one area) or generalized (all over the body). Another manifestation involves the respiratory system and may result in coughing, sneezing, and/or wheezing. Sometimes, there may be an associated nasal or ocular (eye) discharge. The third manifestation involves the digestive system, resulting in vomiting or diarrhea. It is important to keep in mind, that just like in humans, allergies in cats are not curable. However, knowing what your cat is allergic to can help you help them avoid the inciting allergens.
Types of Allergy
There are four known types of allergies: contact, flea, food, and atopy. Each of these has some common expressions, and each has some unique features.
Food Allergy
A food allergy is a condition in which the body’s immune system reacts adversely to a food or an ingredient in a food.
Any food or food ingredient can cause an allergy. However, protein, usually from the meat source of the food, is the most likely offender. Proteins commonly found in pet foods are derived from beef, chicken, lamb, and fish.
Lamb and Rice Diets are not hypoallergenic
Although many people think lamb and rice diets are hypoallergenic, they are not. They are not inherently less likely to cause allergy than other diets. However, they have this reputation. Here is why.
Several years ago there were no cat foods on the commercial market that contained lamb. A manufacturer of prescription cat foods formulated a food from lamb that was suitable for allergy testing, which will be explained below. Because of that situation, lamb-based cat food was considered “hypoallergenic.” If the immune system has not been previously exposed to a chemical, it cannot yet have developed an allergic response to that chemical. However, once past the first exposure in an allergic animal, the immune system is then sensitized and can make an abnormal response, or allergic reaction.
Food Allergy Testing
Cats are not likely to be born with food allergies. More commonly, they develop allergies to food products they have eaten for a long time. The allergy most frequently develops in response to the protein component of the food; for example, beef, pork, chicken, or turkey. Food allergy may produce any of the clinical signs previously discussed, including itching, digestive disorders, and respiratory distress. We recommend testing for food allergy when the clinical signs have been present for several months, when your cat has a poor response to steroids, or when a very young cat itches without other apparent causes of allergy. Testing is done with a special hypoallergenic diet. Because it takes at least 4 weeks for all other food products to get out of the system, your cat must eat the special diet exclusively for 6-10 weeks. If positive response occurs, you will be instructed on how to proceed. If the diet is not fed exclusively, it will not be a meaningful test. We cannot overemphasize this. If any type of table food, treats or vitamins are given, they must be discontinued during the testing period.
The principle is to show that the cat is no longer itching, vomiting, etc. on the novel diet. If there is success, you will be instructed how to reintroduce other food sources to see which ones the cat can consume without reacting. Many owners will elect to keep their cat on the hypoallergenic diet.
Because cats that are being tested for inhalant allergy (atopy) generally itch year round, a food allergy dietary test can be performed while the inhalant test and antigen preparation are occurring.
INSTRUCTIONS for the Food Trial:
Your cat is to exclusively eat a hypoallergenic diet. A prescription food containing hydrolyzed proteins, such as Z/D, is usually recommended. In these foods, the larger protein molecules have been broken down into smaller peptides and amino acids to minimize their allergenic properties. If your cat will not readily eat the prescription food, mix it 25:75 with the current diet for several days, then gradually increase the special diet to 100%. If this does not work, contact us for an alternative plan. Discontinue any chewable treats or vitamins. Table food is not allowed. Offer only distilled water to drink, if that is possible.
Your cat may also be simultaneously treated for atopic allergies. Follow the directions for all medications dispensed.
If your cat has a flea allergy or has enough fleas to make the other allergy problem worse. Flea control is very important and should include treating the cat and its environment. Bear in mind that flea allergies often accompany other types of allergies, especially inhalant allergy.
If your cat has a bacterial skin infection secondary to allergy, antibiotics will also be prescribed. Medicated shampoos and topical treatments may also be recommended.