One of the most common conditions affecting cats that we see at the Animal Clinic at Thorndale is allergy. In the allergic state, the 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 cat). 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. The specific response that occurs is related to the type of allergy present.
Types of Allergy
There are four known types of allergies in the cat: contact, flea, food, and atopy. Each of these has some common expressions in cats, and each has some unique features.
In spite of common belief, a normal cat experiences only minor skin irritation in response to flea bites. Even in the presence of dozens of fleas, there will be very little itching. On the other hand, the flea allergic cat has a severe, itch-producing reaction to flea bites. This occurs because the cat develops an allergic response to the flea’s saliva. When the cat is bitten, flea saliva is deposited in the skin. Just one bite causes intense itching.
Clinical Signs
The cat’s response to the intense itching is to chew, lick, or scratch. This causes hair loss and can lead to open sores or scabs on the skin, allowing a secondary bacterial infection to begin. The area most commonly involved is over the rump (just in front of the tail). This is probably because fleas find this part of the cat more desirable. Many flea-allergic cats also chew or lick the hair off of their legs. Keep in mind that in a true allergic state it only takes one flea bite to set off a massive reaction. You may not be able to see large numbers of fleas or flea dirt and the cat is still extremely itchy.
Treatment
One of the important concepts about allergies, is that they cannot be cured (just like in humans). That said, reducing the exposure to allergens and reducing the reaction to those allergens are the mainstay of controlling allergies. The most important treatment for flea allergy is to get the cat away from all fleas. Therefore, strict flea control is the backbone of successful treatment. There are many products available for flea control, and many work in entirely different manners. In some cases, multiple products may be needed. Some are used on the cat and some in the cat’s environment. All cats and dogs in the household need to be treated with flea control products. Unfortunately, complete flea control is not always possible for cats that live outdoors in warm and humid climates, where a new population of fleas can hatch out every 14-21 days.
Some cats can be desensitized to the adverse effects of fleabites. Flea saliva extract (flea antigen) is injected into the cat in tiny amounts over a prolonged period of time. This is an attempt to reprogram the cat’s immune system so it no longer over-reacts to flea bites. If successful, itching no long occurs or is less intense when the cat is bitten. However, this approach is only successful about 50-75% of the time.
When strict flea control is not possible, antihistamines and corticosteroids (or “cortisone” or “steroids”) can be used to block the allergic reaction and give relief. This is often a necessary part of dealing flea allergy. Some cats respond best to long-acting injections and others to oral medication. Cats are more resistant to the side-effects of steroids than humans, but significant side-effects can occur. For this reason, the goal is to administer the smallest amount of steroid needed to keep the cat comfortable.
Some cats develop a secondary bacterial infection in the skin. When this occurs, appropriate antibiotics must be used. Medicated shampoos and topical medications may be warranted in some situations.