Macarthur Veterinary Group
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Flea Allergy Dermatitis

Flea Allergy Dermatitis (FAD) is one of the most common forms of allergic dermatitis in dogs and cats. It is often the cause of the skin disease that people sometimes refer to (wrongly) as eczema or mange.

A normal dog (or 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 dog has a severe, itch-producing reaction to flea bites. This occurs because the dog develops an allergic response to the flea's saliva. When the dog is bitten, flea saliva is deposited in the skin. Just one bite causes intense itching. You might think your dog has no fleas, but just one bite every 2 weeks can lead to continuous itching.

The dog's response to the intense itching is to chew, lick, or scratch. This causes hair loss and can lead to open sores or scabs, allowing a secondary bacterial infection to begin. Over time, the skin can become black and very thickened. The areas most commonly involved are the tail-base, rump and the backs of the legs. Cats develop multiple small scabs, especially over the neck and back.

Flea Allergy Treatment

The most important treatment for flea allergy is to rid your pet of all fleas. This involves treating your pet directly, treating all in-contact animals and removing fleas from the environment. There are many products available for flea control, and in some cases, multiple products may be needed. For flea allergy we recommend Advantage, used initially every 2 weeks, then reducing to monthly once the problem is under control.

Initially, or when complete flea control is not possible, corticosteroids (such as prednisolone) may be recommended to block the allergic reaction and give your pet some relief. Antihistamines are usually not effective.

Please refer to our Flea Control page for more information on flea control.