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Vet Advice: Dog Flea Allergy and What to Do About It

Don’t panic — there are simple steps you can take to prevent and treat flea allergy in dogs.

by Sara Greenslit, DVM
September 13, 2021
Black puppy itches behind her ear due to flea allergy
Christian Müller/Adobe Stock

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If your dog has fleas, the first thing you may notice is hair loss along their neck, spine, and thighs. Their skin may also be flecked with scabs and hot to the touch. Then, of course, there’s the scratching: automatic, back-foot-reaching, irrepressible itching. You may — or may not — see live fleas; it’s possible you’ll only see flea dirt (specks of digested blood).

Often, a client will say to me, “But my other cat/dog is just fine.”

That’s the thing — not all pets are allergic to fleas. But for the ones who are, the suffering can be extreme. As anyone who’s gotten a mosquito bite knows, itching causes a distinct, crazy-making distress. The good news is, it’s actually pretty simple to prevent and treat fleas. Here’s how.

First of All, What is Flea Allergy in Dogs? 

Flea allergy dermatitis (FAD) arises when your dog’s immune system overreacts to flea saliva. The severity of the itching doesn’t necessarily correlate to the number of flea bites your dog has; sometimes, it only takes a few to generate a whole lot of scratching. Many dogs will also have secondary bacterial and yeast infections, as well as environmental allergies, all of which aggravate the itch.

Flea Allergy Symptoms

  • Itchy skin causing excessive scratching

  • Fur loss

  • Thickened skin

  • Redness

  • Hot spots

  • Restlessness

  • Scabs or crusts

How Do You Prevent Flea Allergy Dermatitis in Dogs?

According to William Oldenhoff, DVM, DACVD, a dermatologist at LeadER Animal Specialty Hospital in Cooper City, Fla., there are several different steps you need to take. The first is to use a flea preventative year-round, which takes a while to resolve the infestation because the flea life cycle ranges from one to two months, depending on environmental conditions, and pupa can survive for up to a year before becoming adults.

Dr. Oldenhoff also recommends cleaning your house thoroughly. “Vacuum all surfaces, paying particular attention to the areas adjacent to walls and corners and under furniture,” he says. “Be sure to clean the furniture as well, and launder any bedding the dog sleeps on.” He does not recommend having the house itself sprayed or otherwise treated, since flea preventives and meticulous environmental cleaning are usually enough to keep fleas at bay.

How Do You Treat Flea Allergy Dermatitis in Dogs?

To relieve the itch, Dr. Oldenhoff recommends oral meds such as oclacitinib or steroids. However, he cautions, just because your dog stops their mad scratching, that doesn’t mean the fleas are gone. “When these therapies are prescribed, your pet will be feeling much more comfortable, but the flea infestation is still present, and thus flea control must still continue,” he notes.

Other flea allergy dermatitis treatment options include medications for secondary bacterial and yeast infections and a dewormer for tapeworms. Fleas harbor dipylidium caninum larvae (aka, the flea tapeworm). If an infected flea is ingested — for example, as the dog grooms himself — the larvae develop into adult tapeworms in the dog’s intestines. The good news is, treatment for tapeworm is simple and effective (your vet will most likely prescribe an oral medication called praziquantel). 

Ask a Vet

Sudden scratching? Finicky food eater? Loose poop? Whatever pet health question is on your mind, our veterinary pros are here to help.

Can Fleas Become Resistant to Flea Products? 

If flea control depends on flea products, and these have been used for many years, do fleas develop resistance? Hypothetically, they could. “In theory, resistance would be more likely with the products that have been on the market longer,” Dr. Oldenhoff says. “For this reason, I have recently been recommending the new oral flea and tick preventives,” among them, Nexguard, Bravecto and Simparica (isoxazoline acaricide/insecticides, only for use with dogs). 

Dr. Oldenhoff recommends these products because they are virtually foolproof. You don’t have worries like: “Did I put the full vial on my dog? Did I get it right on the skin? Did I bathe my dog too quickly, thus washing it off?” (Note that isoxazolines are only available by prescription and require an annual exam to be renewed.)

A dog’s perceived resistance to flea products may also be the result of their exposure to feral cats and urban wildlife, or to other pets in the household (all of whom need to be treated year-round); otherwise, the infestation will continue.

Are There Natural Ways to Treat Flea Allergy in Dogs?

If you’re looking for a natural solution to a flea infestation, know that “natural” does not necessarily mean “non-toxic” or effective. Some people use diatomaceous earth or boric acid in their homes, particularly on carpet and around baseboards. These pesticides may kill some of the larvae to reduce the overall flea population, but it won’t be enough to gain full control of an infestation. The products can be harmful if applied directly on animals, as well.

Both diatomaceous earth and boric acid have effects on humans and animals. Diatomaceous earth, a type of silica, can be an irritant to the eyes, skin, and respiratory tract. Boric acid can be corrosive to the eyes and skin, cause vomiting and diarrhea, respiratory difficulties, and (in large quantities) seizures and coma. You can take steps to reduce you and your dog’s exposure to these natural pesticides during their application, but in the end, basic house cleaning is your best tool against fleas.

You’ll also see flea collars made with essential oils. These collars are sold as unregistered repellants and not true insecticides, so the Environmental Protection Agency doesn’t require their manufacturers to provide data regarding their usefulness. (Cats are especially sensitive to essential oils, so proceed with caution.)

Other integrative options include allergy shots and fish oil. Because they’re based on your dog’s specific tested allergens, allergy shots may help with their concurrent atopy (the likely genetic tendency to develop allergic diseases)—but they will not directly affect flea allergy dermatitis. 

Adding fish oil to a dog’s diet after initial treatments may help control flea allergy dermatitis by reducing inflammation. But applying oils — such as coconut oil — directly to the skin isn’t recommended. “I have seen animals with microbial overgrowth that I suspect was exacerbated by coconut oil application,” Dr. Oldenhoff says.

A flea infestation can cause physical and emotional stress on everyone. No one wants fleas — not you and not your dogs. To keep your home flea-free, the best thing you can do is clean often. Pull out your vacuum — and if your dog runs away, tell them it’s for their own good!

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sara greenslit

Sara Greenslit, DVM

Sara Greenslit, DVM, CVA, is a small-animal veterinarian and writer who lives and practices in Madison, Wisc.