There are 3 different types of allergies seen in pets: fleas, environmental (atopy) and food. We will focus in this article with the flea allergy dermatitis (FAD).
Flea allergy dermatitis is a hypersensitivity to an antigen present in flea’s saliva. Once a patient shows a hypersensitivity to flea bites, the allergy will always be present. In most cases it becomes more severe with each successive flea infection.
Animals with FAD are generally older than 6 months, are itchy and have skin lesions that are crusty, red and pimple like lesions may be present. Fleas and flea dirt are not always needed to make a diagnosis of flea allergy dermatitis since patients can show reactions after only one flea bite. Cats, especially, are such avid groomers that often on examination there are no fleas or flea dirt to be found.
Diagnosis can be based on the appearance and distribution of the skin lesions. On dogs lesions are localised to the lower back near the base of the tail, inner thighs, abdomen and neck. With cats the lesions are usually found on the back of the neck, abdomen and lower back.
Treatment for FAD is flea control as well as an oral medication to control the itchiness. The most effective medication is a short course of steroid to calm the inflammatory response. For animals that have shown a flea allergy in the past it is advised to maintain these animals on flea prevention for the entire Canadian flea season.