Flea Allergic Dermatitis in Dogs

By: Alex Betzen, DVM

TVMA Member
Houston, TX.

Published June 2016

In Texas, the heat and humidity allows for a nearly year-round flea season. Fleas (Ctenocephalides felis) are the most common external parasites seen on dogs, and flea hypersensitivity and flea allergic dermatitis are some of the most common skin conditions in dogs. For dogs that suffer from flea hypersensitivity and flea allergic dermatitis, flea control is vital. Dogs with flea allergy dermatitis have an abnormal immune response to fleas and fleabites. What ultimately causes dogs to become so itchy from fleas is that they are allergic to the saliva from the flea. When dogs have a flea hypersensitivity or allergy, one bite can make them extremely itchy for days. They will often scratch and chew to the point of having a bacterial skin infection, which makes them even itchier.

Dogs with these conditions will generally have the worst skin lesions at the base of their tails and down their backs. Other clinical signs of flea allergic dermatitis include hair loss, secondary skin infections and itchiness over the hips and backs of the thighs. Your veterinarian will prescribe a flea treatment protocol, involving appropriate flea control and environmental treatments.

Flea Control

In terms of environmental factors, most of the year it is not cold enough to kill fleas in the environment outside. However, fleas can happily live in our indoor environments all year long. All animals in the household control in addition to dogs and cats with flea allergy dermatitis. If there is an animal not on flea control, it can serve as a source of fleas for the animals with the allergy.

There are several different types of flea control products, and with a severe infestation, you may need to use more than one product. Prior to your veterinary visit, consider whether you prefer an oral or topical medication. The frequency of bathing and how the product is applied can greatly affect the efficacy of the product if you use a topically applied medicine. The new generation of flea products as well as the combination flea-heartworm medications do a great job in flea control when used according to directions.


Luckily, we have effective treatment options available to animals with flea allergy dermatitis. To relieve itching, veterinarians may prescribe medicated shampoos, topical medications and/or oral medications. Common oral medications for itching in dogs and cats are antihistamines and corticosteroids. Many of these patients will have secondary bacterial or yeast infections, so antibiotics and medicated shampoos may also be necessary. Finally, your veterinarian will discuss flea control products specific to you and your pet’s needs; this is the most important aspect of treatment for animals with flea allergy dermatitis. With appropriate flea control, we often achieve success with these patients long-term and avoid year-round oral medications.

Alex Betzen, DVM, is a graduate of Kansas State University College of Veterinary Medicine, who practices at Westbury Animal Hospital in Houston, Texas.

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