Flea Bite Allergy

Flea Bite Allergy is also called Flea Allergy Dermatitis. While the latter name sounds like a patient is allergic to the very presence of fleas, that’s not actually the case.

Flea Bite Allergy (FBA) is actually an allergy to the saliva of the flea. No, fleas are not expectorating on your pet, making him itchy.

Fleas, like mosquitos, feed on blood. And, like mosquitos, fleas possess a feeding mouthpart called a proboscis. The proboscis is actually a feeding tube the female of the species uses to pierce the skin of its victim to access the bloodstream. Both species have been given an anticoagulant saliva, saliva that stops the blood meal from clotting. That saliva is injected into a dog, cat or person prior to feeding, lest clotted blood stop up the feeding tube, which would cause the insect to starve to death.

In 90% of pets a bite from a flea is a non-event. However, about 10% of the dog and cat population has the ability for the immune system to recognize flea saliva as containing foreign proteins, proteins that don’t belong in the pet’s body, then have an allergic reaction to the saliva.

In dogs, that reaction takes the form of an itching sensation that is typically centered around the head of the tail (where the tail meets the trunk of the body). The itchiness can extend down the back legs, in between the back legs and up the trunk as far as the ribs.

In cats the pattern may be identical, or a similar condition called Eosinophilic Granuloma Complex may be initiated.

It is important to recognize that it doesn’t matter where the flea bites the pet. The reaction is systemic, controlled by an aberration of the immune system, so even if the flea’s bite is on the nose, the itching sensation is still perceived in the areas described above.

It is also crucial to remember that one bite from one flea can stimulate this allergy for up to a week. The level of itchiness is proportional to the quantity of flea saliva injected, so there is ten times as much itchiness with ten flea bites as with one.

Treatment of this allergy is unique in that medication is a secondary means of control. It is almost impossible to give enough allergy-blocking medication to an FBA patient if fleas are allowed to continue to bite. Therefore, flea control is our first line of defense for controlling Flea Allergy Dermatitis (FAD).

Depending on where you live, and the attendant level of flea infestation in your area, medication to control allergies may be dispensed in addition to flea-controlling medicines. For example, in the Deep South, where we have flea infestations year-round, even with our best efforts at controlling fleas our pets are subject to the occasional flea bite. By maintaining four seasons of allergy-blocking medication, reactions can be kept to a minimum.

Many FBA patients also have Atopy, or Allergic Inhalant Dermatitis, and certain oral medications are extremely effective in controlling that type of allergy.

For our recommended methods of preventing and controlling fleas, click here.

As with other allergies, FBA patients commonly have secondary complications, such as bacterial and/or yeast infection of the skin. If those complicating factors are present, they must be addressed by your pet’s doctor.

Another common characteristic among pets with allergies is the tendency to have relapses or breakthroughs. Despite your best efforts to do everything exactly right, at times your pet is going to have episodes that require intervention by your veterinarian.

It’s just the nature of dermatology.



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