Flea bite hypersensitivity and flea allergic dermatitis is the most common skin disease in pets. And although the allergies usually develop when dogs are young (less than one and up to five years of age), flea allergies can begin at any age. It is the saliva from the flea that is actually believed to be the cause of the allergy or sensitivity.
The flea life cycle includes the adult flea, egg, larva, and pupa. Adult fleas do bite but cannot survive long if they are not on the dog. Once the adult flea lays its eggs on the host it will fall off, leaving the eggs to mutate through the rest of their life cycles. This generational process continues on the host pet until the flea population has been eradicated entirely.
The condition described in this medical article can affect both dogs and cats. If you would like to learn more about how flea bite hypersensitivity and flea allergic dermatitis affect cats, please visit this page in the PetMD health library.
Symptoms and Types
Flea bite hypersensitivity or flea allergic dermatitis usually causes severe itching of the skin. This condition is medically referred to as pruritis. As few as one or two flea bites a week can cause pruritis, so symptoms will often persist even after some form of flea control has been used. Symptoms are often episodic, but most dogs will have symptoms that worsen with age. Some dogs can also suffer behavioral problems as a result of flea bite hypersensitivity, with a condition called neurodermatoses.
Most owners first notice frequent and severe itching and scratching, hair loss, and scabs on the dog's skin. Many times the hind end is affected more than the front of the body or the head, however, dogs that are being affected by an allergic reaction to the fleas can have lesions anywhere on the body. Moreover, fleas or flea dirt may or may not be visible.
By using a flea comb to inspect your dog's hair, fleas or flea dirt can be seen more readily. Skin tests for mites or bacterial skin diseases may be recommended if fleas cannot be found. Sometimes the best diagnostic method is to just treat for fleas.