CVMA-ACMV

Pets Can Become Allergic to Flea Bites

October 23, 2012

Flea Allergy Dermatitis, also termed flea-bite hypersensitivity, is an allergic skin reaction to flea saliva. It can occur in both dogs and cats when fleas bite them. Dogs and cats rarely get this form of allergy before six months of age. Usually, the age of onset is around three to six years of age. The primary clinical signs of this skin disease are severe itching, biting, and scratching, usually involving the hind end, especially at the base of the tail or inside the thighs. Cats often have an itchy patch over the base of the tail or in their thighs, but may also scratch around the head and neck region.

Diagnosis is by physical examination, and in cats, it may also be associated with an increased eosinophil (a type of blood cell) count. Note that in cats, it can be difficult to find fleas or flea dirt, especially in longhaired breeds. Some cats are exquisitely sensitive, and even one can cause significant itchiness and skin lesions, so there may not be any found on them.

This type of allergic dermatitis is managed by eliminating exposure to adult fleas and by providing symptomatic therapy to help increase pet comfort while inflammation in the skin subsides. Flea control is accomplished by using an adulticide (i.e., a product that kills adult fleas), such as a flea powder, spray, topical agent, oral preparation or foam. Flea shampoos tend to be minimally effective in preventing fleas since most of the insecticide in the shampoo is washed off with the final rinse, but does provide a quick kill of resident fleas. 

There are currently several topical adulticides available from your veterinarian that are given orally, are injected, or applied directly onto the pet and that have been shown to be highly effective and safe to apply. Thorough control of fleas may include environmental treatments. In addition to the home, outdoor areas need to be treated in warm seasons. There is no cure for flea-bite hypersensitivity itself, so as long as fleas are present, the pet will have problems. Those pets that are affected may also become more reactive as time goes on. Medications may also be needed to help soothe the irritated skin and clear up any secondary infection (dermatitis). Your veterinarian should be consulted to determine which treatment option is best for your pet based on its lifestyle, activity level, and environmental contacts.

Note that fleas can transmit a type of tapeworm intestinal parasite, so a stool sample should be checked from flea-infested pets to make sure that they are not afflicted with this worm as well.