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Flea Allergy Dermatitis in Dogs

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Updated: April 25, 2018

What is flea allergy dermatitis?

Flea allergy dermatitis is a condition that affects both cats and dogs. Severe, prolonged itching in both cats and dogs, and an often-significant increase in grooming in cats are noticeable signs of the condition. Many pet owners are shocked to find out that flea allergy dermatitis can result from even very minimal and intermittent exposure to fleas – these pets are that sensitive and each flea may bite 50 times per day.  And because fleas can live year-round in many environments, cases of flea allergy dermatitis can be seen at any time of the year.

What does flea allergy dermatitis look like?

The skin condition looks a bit different in dogs and cats. Dogs tend to show hair loss, skin thickening, redness, and sometimes “hotspots” over the rump and tail head. These signs may extend to their thighs and abdominal area. On the other hand, cats may have normal-looking skin with hair loss due to excessive licking, usually over the back and around the neck. Some cats also develop tiny red crusts over the back.

Listen to episode 1 of the Paws & Play with Dr. J podcast: How to help cats and dogs with allergies

Why does flea allergy dermatitis develop?

Flea allergy dermatitis occurs in pets that develop a hypersensitivity (allergy) to flea saliva. When these pets are bitten by a flea, the itching that results from the injection of saliva is much more severe and prolonged than what “normal” pets experience. While some dogs and cats can easily tolerate a moderate number of flea bites each day, flea-allergic pets do not!

How is flea allergy dermatitis diagnosed?

The diagnosis is made on the basis of clinical appearance. If we find fleas, or flea “dirt”, we can be certain of flea exposure. In many cases, only the skin lesions are seen because the flea bites can be so intermittent. Flea-allergic cats are particularly effective at removing fleas from their skin by eating them.

How is flea allergy dermatitis treated?

The most important part of treatment is reducing the number of flea bites. And for treatment to be most effective, all dogs and cats in the household must be on a consistent and effective flea prevention product, even if only one pet is displaying the symptoms of flea allergy dermatitis.

Several highly effective flea control products are available and outlined below. Most are designed for once monthly use, and the dose for all of them is determined by the weight and age of your pets. Always speak with your veterinarian or a board-certified veterinary dermatologist to ensure that you are choosing the most effective, and safest flea product(s) for your pets and your home.

Topical products:
Products that are applied directly to the skin include Vectra® 3D, Revolution®, Advantage®, and Frontline®.Some of these come in various formulations that differ in their effectiveness against parasites other than fleas (ticks, mites, heartworms, roundworms, etc). Except for Revolution®, which is absorbed through the skin, all of these topical treatments will be less effective with frequent bathing, especially with shampoos that remove oils from the skin.

No topical products that are labeled and designed for dogs should ever be applied to cats – this is especially true for any of the products that contain pyrethrin or permethrin.

Chewable Pills:
Comfortis®, Trifexis, and NexGard® are chewable tablets that are absorbed into the blood stream and are the quickest at killing fleas.  Each of these products are administered monthly and are excellent choices for flea allergic pets that are bathed more than once monthly.

Additional treatments:
The itching can take a while to subside even after the fleas are gone, so some pets benefit from additional anti-inflammatory medications. If the skin is infected, antibiotics (such as Convenia®, Simplicef®, or cephalexin) may also be prescribed.

Shampoos and conditioners can soothe the inflamed skin, and if they have been recommended, be sure to follow the directions of the flea control product with respect to application following bathing. In most cases, it is best to separate the application of a topical flea control product from bathing by at least two days.

Final words on flea allergy dermatitis in cats and dogs
Treatment for cats and dogs suffering from flea allergy dermatitis can be effective, and will go a long way towards improving your pet’s quality of life. The best goal for pets with this condition though is prevention of flea bites. and the best way to prevent flea bites is year-round, veterinarian-prescribed, comprehensive flea control – on all of your household pets.


Topics: Cat Health, Dog Health, fleas on dogs, Fleas on Cats, Flea Allergies, Dermatitis

Please do not ask emergency or other specific medical questions about your pets in the blog comments. As an online informational resource, Preventive Vet is unable to and does not provide specific medical advice or counseling. A thorough physical exam, patient history, and an established veterinary-patient-client relationship is required to provide specific medical advice. If you are worried that your pet is having an emergency or if you have specific medical questions related to your pet’s current or chronic medical conditions, please contact or visit your veterinarian, an animal-specific poison control hotline, or your local emergency veterinary care center.

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