Fleas are parasites that subside on the blood of mammals like dogs and cats, though they can live on other host animals as well. They have a life cycle of about six to twelve months, and fully formed adult fleas can survive for long periods without the blood of a host. When an adult flea finds a home on your dog, however, it won’t likely be fasting.
The flea’s mouthparts have evolved to penetrate the skin of a dog, especially the thin epidermal area around the abdomen and flanks. When a dog is bitten by a flea for its blood meal, some of the flea’s saliva is injected through the dog’s skin layer, like backwash. Flea saliva is what causes the skin allergy in dogs. The dog reacts to some of the antigenic materials in the saliva, such as amino acids, aromatic compounds, phosphorus, and polypeptides. The dog’s immune system reacts to these materials by producing antibodies.
Once the flea bites an allergic pet, the dog will react in a more pronounced manner than a dog not allergic to fleas would. A small bump and redness may appear, and the bite will be extremely itchy. Even one or two bites will create a constant itching in the dog for days, while a non-allergic dog can be bitten several times until it feels the effect of the flea bite.
Flea allergies may have a genetic component, but these allergies are not predisposed in certain dog breeds or genders. Flea allergies can begin as early as one year in age, and generally start when a dog is young. Dogs of any age, however, can develop hypersensitivity to flea saliva, and conditions will worsen with age.
If you discover a flea infestation in your home, recognizing a flea allergy may not be obvious at first since all dogs will react to flea bites to some degree. Your dog’s behavior and a prominent skin condition could indicate a flea allergy is present.
This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.