Flea allergy dermatitis (FAD) is probably the most common cause of skin problems in dogs and cats. It is due to an allergic reaction of the pet to the saliva of the flea. This saliva is released (and enters the pet’s skin) each time the flea feeds.

The predominant clinical sign associated with FAD is itching. In most flea allergies, itching begins within 30-45 minutes after the bite. The cat often rubs and scratches his (her) back end. The lower back, the neck , the base of the tail, and the abdomen are areas that are commonly affected.

When scratching begins, the skin turns red. After long bouts of rubbing and/or scratching, hair loss becomes significant. In long-term cases, the skin becomes crusty, and thickened. Self mutilation can be so extensive that a secondary bacterial infection may develop.

Cats with flea allergies often develop a skin condition called miliary dermititis. Lesions associated with miliary dermititis are most pronounced is the neck and lower back. The lesions consist of papules that eventually develop into crusts. The crusts are usually felt when the animal is caressed or groomed.

In warm, humid areas, flea season is year round. In the northern United States, where the winters are generally long, flea activity ceases between November and May. During the cold weather, the pupal stage remains dormant. In late spring, when the temperature begins to rise, the adult fleas emerge and find their way to our pets. (See article: Biology of the Flea)

Fleas do not have to be seen in order to diagnose a flea allergy. Since the allergic reaction may be due to a single flea bite, fleas may not be present. In a multipet household, some animals may be loaded with fleas while others have very few. There is an individual tendency for certain cats (and dogs) to attract fleas. (Hence the term “fleabag”)

A Flea - Magnified

A Flea – Magnified

In cats, fleas are most commonly seen around the base of the tail. When fleas are suspected but not seen, the presence of “flea dirt” may aid with the diagnosis. “Flea dirt” is the excrement of the flea and it consists mainly of dried animal blood.

Effective flea control requires treating all pets as well as the environment. Pets and infested areas must be treated on a regular basis. (See article: Flea Control)

Anti-inflammatory medication is useful for reducing the allergic response associated with the flea bite.

Use caution when selecting a flea product for your cat. Certain products that are routinely used for dogs are extremely toxic for cats.

Your veterinarian will recommend the products and treatment schedule that is best suited for your cat(s).