Flea bite hypersensitivity (FAD)

FAD, or flea bite hypersensitivity, is a reaction to the bite of a flea. When a flea bites and dog or cat (or human) it injects a small amount of saliva into the skin. Normally this produces little more than a mild itching. Some cats and dogs can develop an allergy to this saliva, and, in these animals, even a single flea bite can cause intense itching and irritation. A severe flea infestation, where lots of fleas or flea dirt is found, can cause the same signs in non-allergic patients.

FAD is most commonly seen in the summer months when fleas are more prevalent but can occur even in winter because even low numbers of fleas can cause a reaction. Pets suffering from flea bite hypersensitivity will bite, chew and lick their skin continually.

Clinical signs:

Dogs typically attack their back, just above the tail, the back and insides of their hind legs, their belly and around the anus. This leads to scabs, hair loss, thickening and increased pigmentation of the skin and scaling and, eventually, to weepy skin and sores.

Cats are affected slightly differently. Some cats develop small scabs over their back or, in severe cases, over their whole body called ‘miliary dermatitis.’ Others lick until they develop bald patches, especially on their belly and the back of their hind legs.

How is FAD diagnosed?

Diagnosis is usually easily made by a visual examination. Conditions other than flea bites may cause similar signs, however, so we may recommend tests to confirm the diagnosis, especially when there is no evidence of fleas.

Treatment protocols:

FAD is not life threatening, but nor is it curable. In the short term, hypersensitive pets who have been exposed to fleas and are suffering from FAD need medication to relieve the itching, stop them scratching and give their skin a chance to heal. Some will also need antibiotics for infections that have developed in the damaged skin.

In the long term, all pets suffering flea bite hypersensitivity need to have their exposure to fleas minimised — permanently.

There are several excellent, easy to use products available that effectively kill adult and juvenile fleas both on your pet and in the environment. Where large environmental contamination with flea eggs exists separate environmental treatments may be recommended.

Other pets in the household also need constant treatment. Although they may not be allergic and no be affected, they do carry fleas which then can bite the affected pets. Please talk with our nurses regarding a specific flea prevention treatment program for your pets.