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Itching and Allergy in Cats
Revised: April 26, 2018
Published: July 16, 2007

Photo by Dr. Teri Ann Oursler

Coping with an itchy cat can be an extremely frustrating experience for you, the pet owner, and can truly test the limits of the human-animal bond.  Persistent scratching and chewing by the pet can also result in open wounds to the skin and pain to your cat.  The following information is intended to help provide pet owners with a basic understanding of the most common underlying causes of itching and allergies in small animals.

What are the most common causes of chronic itching?

Itching in cats can involve not only scratching but also chewing, licking and rubbing. The common causes of itching in cats are a type of fungal infection called ringworm, external parasites such as fleas and mange, and allergies.

In itchy cats, we do some culture tests for ringworm, so we can be sure that is not the problem. We often recommend therapeutic trials for mange in chronically and severely itchy cats.  We always recommend stepped-up flea control and monitoring for fleas, as flea infestation can really make allergy worse!

What are allergies?

Allergies are a common cause of skin conditions in cats. People with allergies usually have hay fever (watery eyes, runny nose and sneezing) or asthma. Although cats with asthma can be allergic, most cats with allergies lick or chew their fur.

What are the major types of allergies in cats?

Flea Allergy
Flea allergic dermatitis is the most common skin disease in cats.  For the flea allergic patient, 100% flea control is essential for remaining symptom-free. 

“But doctor, I never see fleas on my pet.”  You may not see them, but that doesn’t mean they aren’t there!  Flea allergy is caused by the flea’s saliva, and it only takes a few bites to cause a problem.  Also, the itchy pet often scratches or licks so much that adult fleas are hard to find because they are removed from the body.

“If fleas are the problem, why is my pet still itchy in the winter?”  In warm climates or in our homes, fleas may survive in low numbers year-round.  Because flea allergy is so common, many veterinarians recommend instituting complete flea control before proceeding with test for itching. For most allergic pets, year-round flea treatment is an important part of reducing itch.

Food Allergy
Some pets develop hypersensitivities to foods. Various food proteins, carbohydrates, or even preservatives or dyes can all be potential food allergens. There is currently no accurate blood or skin test to determine if your cat has a food allergy. The only method of diagnosing a food allergy is by placing your pet on a carefully selected prescription or homemade hypoallergenic diet for several weeks, which is called a food trial. The diet only contains ingredients your pet has never eaten before. If the allergy signs resolve, a food challenge is performed by feeding the former diet and watching for a return of the itching.  If this occurs, a diagnosis of food allergy is confirmed.

Atopic Dermatitis
Atopic dermatitis (AD) is an inherited predisposition to developing skin problems from exposure to a variety of commonplace and otherwise harmless substances including the pollens of weeds, grasses and trees, as well as house dust mites and mold spores.  In cats that have been diagnosed with AD, allergy testing by intradermal skin testing or in vitro blood testing can identify what a pet is allergic to in the environment.  Evaluating the results of these tests helps us compile a list of allergens for a “vaccine” to decrease the pet’s sensitivity. 

Secondary Infections
Allergies are often the underlying cause of recurring skin and/or ear infections.  Bacterial and yeast infections, though secondary to the allergy, can increase your pet’s level of itching.

Can allergies be cured?

Unfortunately, there is no cure for allergy and it is usually a life-long problem. We seek to control allergies and improve the quality of life for both you and your cat.  We will formulate the best program of management that suits all involved with your cat’s care. 

Can itching be treated without the expense of diagnostic testing?

There are many anti-allergy medications to reduce itching.  These medications do not cure allergies but can help decrease the symptoms. However, without addressing the underlying cause of the allergy, the itching will return when the medication is stopped.  Long-term use of some anti-allergy medications, such as steroids, can result in many health problems.  Working with your veterinarian to diagnose the underlying cause of the allergy and itching may reduce the need for medications or enable your veterinarian to use more specific and targeted allergy treatments.

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