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.
Flea control and prevention is essential for dogs with flea bite hypersensitivity. There are numerous options on the market that kill the adult fleas for a period of time, but all should be repeated (as indicated) for continuous flea control. Insecticides often are applied as spot-on treatments - typically topical treatments that are applied to a small area, usually at the top back of the neck where the dog is unable to lick it off. Oral products are also available, some of which may be more useful and practical for you and your dog. Flea shampoos can also be beneficial for young animals or for an acute flea infestation, but continuous management with one of the long-term products is essential.
Flea control for outdoor pets is virtually impossible, but current flea control products that are available may be sufficient for short term treatment, as long as the house does not become infested. There are many pet products that can be used to treat for fleas during their immature stages of life (i.e., eggs). However, if the house or yard has an infestation, environmental treatment will be necessary. Fleas will actually bite humans in the house if flea medications cause them to leave their animal host to search for another host.
Dogs that are allergic to fleas may require steroids or antihistamines to combat their sensitivity to the bites. Likewise, if a secondary bacterial infection develops as the result of open sores, antibiotics may be prescribed. Follow-up exams are often necessary to determine how treatments are progressing.
Living and Management
The most important factor in managing a dog with fleas is the application of regular doses of flea treatment on a timely basis. Because it takes only one or two bites for a flea allergic animal to start itching, it is best that you be consistent with flea control products. Other factors to consider, such as frequent bathing, and whether you are using spot-on treatments or other topical products, will determine how long to wait between product applications.
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