flea allergy dermatitis

Flea Allergy Dermatitis

Tiny insects crawling on your skin and biting to feed on your blood… it’s really no-one’s idea of fun at the best of times, but for some poor pets, fleas are more than just an irritation! Dogs and cats can be allergic to these irritating critters! For these pets, just a few flea bites can lead to a severe, very itchy, skin condition, called Flea Allergy Dermatitis, or FAD.

But how do you know if your pet is allergic to fleas? We’re here to tell you all you need to know about this common condition, and to share the best ways to help keep your pets protected against these annoying pests. 

flea allergy dermatitis

What is FAD?

FAD is a skin condition of dogs and cats caused by an allergy to flea bites. The allergy is actually triggered by a component of flea saliva, which, rather disgustingly, is injected into your pet by the flea as they feed. Flea bites are irritating to whoever’s unfortunate enough to be on the receiving end of them, but in our flea-allergic pets, just a few bites are enough to trigger a cascade of chemical reactions in the skin, resulting in this very sore and itchy skin condition.

flea allergy dermatitis
What are the symptoms of FAD?

First and foremost, dogs and cats with flea allergy dermatitis or FAD for short, will be itchy. And we don’t just mean a slight tickle, the allergy triggers intense itching, and causes our four-legged pals to bite, scratch, chew and lick themselves to try and get some relief.

In dogs, FAD typically affects the skin around their thighs, groin, lower back and the base of their tails1 (it’s sometimes called a “pants distribution ” – imagine your pooch wearing a pair of pants, that’s the area usually most affected!). The skin often looks red, sore and crusty, and you may also notice some areas of fur loss. If the condition progresses, areas of the skin can become pigmented, and your pup may also develop a skin infection as a secondary response to the skin barrier being damaged.

Cats  with FAD often get a bumpy rash in response to the allergy; when you stroke your feline friend this can feel like small sand-like grains on the surface of their skin. This rash is often found over their back, neck and face1, but these lesions aren’t specific to FAD, other allergies can cause similar signs. You may also notice your moggy is over-grooming, which can lead to broken hairs, loss of fur, and red, sore areas of skin.

How do vets diagnose FAD?

You might think that finding fleas on your pet would be the most obvious way to diagnose the condition, but actually pets are great at removing any evidence of fleas when they groom themselves, so spotting them can be tricky! It’s worth remembering, too, that it only takes a few flea bites to trigger the allergy, so finding the culprits can be almost impossible. 

Although fleas themselves might not be visible, something else might be- and that’s flea dirt! Flea dirt (a slightly nicer term for what is essentially flea poo!), is produced by fleas after they’ve fed on your pet, and resembles small grains of black pepper. Your vet may run a flea comb  through your pet’s fur, and shake the contents onto a wet, white tissue. Flea dirt will turn red when it comes into contact with the water (due to the fact that it’s made up mainly of undigested blood- lovely isn’t it?!), confirming that fleas have, indeed, set up residence on your pet.

If your vet suspects that FAD may be the cause of your pet’s condition, they may suggest trialling some flea treatment as a first step.


How is FAD treated?

Treatment is, thankfully, relatively straightforward! As we’re sure you’ve guessed, pets with FAD will need flea treatment to kill the critters that are causing the problem. Your vet may also prescribe some additional treatment aimed at helping to soothe and heal your pet’s skin.

Fipnil Plus  makes treating fleas simple! It is an easy-to-apply spot-on treatment available for both dogs and cats, that kills both fleas and ticks. It also has the added bonus of stopping the development of all of the flea life stages, even those within the home.

While we’re on the subject of the home; if your pet has fleas, you may also need a treatment for your house, as well as for your four-legged pal. That’s because these pesky parasites don’t just confine themselves to your pet; fleas lay eggs which fall into your home, and develop into larvae, and then pupae, from which new adult fleas emerge. Your vet can recommend a household flea spray to use on your home, to target these stages.

Alongside the flea treatment, your vet may advise some other medication, too. Antibiotics may be needed if your pet’s skin is infected, and specialised shampoos can be useful too. Your vet may also prescribe a steroid medication, which can help settle down that annoying itch.

flea allergy dermatitis

Preventing future flare ups

Treating flea allergy dermatitis is one thing, but all it takes is for your four-legged friend to meet a few more of the critters when they’re next exploring outside, and the problem can flare up all over again! Flea protection is important for all pets (allergies aside, fleas can cause a number of other issues, including transmitting diseases and even passing a tapeworm onto your pet!), but if your dog or cat has a flea allergy, ensuring there’s not even a small window of opportunity for fleas to take hold is extra important.

Thankfully, keeping pets protected throughout their lives is less daunting than it sounds! Fipnil Plus can be used on an ongoing, monthly basis to offer continued protection against fleas and ticks.


What’s the outlook for pets with FAD?

Fortunately, by keeping up with regular flea treatment, pets with flea allergy dermatitis can live normal, happy lives. If your pet does have a flare-up, then visiting your vet straight away will help you get on top of the problem before it gets worse. 

As if creepy crawlies living on your skin wasn’t bad enough, having an allergy to these critters can spell misery for our pets. Thankfully, managing your flea-allergic four-legged family member is straightforward. Keeping up with regular flea treatment throughout your pet’s life will help them steer clear of this itchy condition, and help protect them against other effects of these irritating pests into the bargain!




  1. Elsheikha, H.M. Flea allergy dermatitis: the continued challenge.  The Veterinary Nurse, July 2012.