When Your Pet Has a Flea Allergy


Reviewed by Amy Flowers, DVM on March 07, 2019 From the WebMD Archives cat scratching itself

Fleabites make most pets itch. But some dogs and cats are allergic to the pests. Your doctor may call this flea allergy dermatitis (FAD) or fleabite hypersensitivity. If your pet has a flea allergy, “even one or two fleabites can make your pet miserable,” says Carol Osborne, DVM, a veterinarian at Chagrin Falls Veterinary Center in Chagrin Falls, OH.

Many cats and dogs are allergic to fleas. In fact, FAD is the most common skin disease in dogs in the U.S. Flea allergies often spike in the summer, and pets that have seasonal allergies are more likely to have an allergic reaction to fleabites. But any pet can get FAD.

Plenty of things can help.

Spot the Signs

When a flea bites your dog or cat to draw blood, it injects saliva into your pet’s skin. Flea saliva is irritating to most animals, including humans. But the compounds in it can trigger an allergic reaction in some pets.

Everyday itching from a fleabite isn’t the same thing as a flea allergy. If your pet has FAD, the itching will be intense and last longer.

“Your pet may itch for up to 2 weeks after a bite, and the itching will be severe and even damaging to your pet’s skin,” Osborne says.

Other signs of FAD include:

  • A rash on your pet’s skin or raw, irritated, or bleeding areas on your pet’s body. Dogs usually have it near their back legs, stomach, or tail area. Cats are more likely to have it near their neck and face. 
  • Hair loss, especially in areas where the bites happened
  • Small red or pink raised bumps that may look like pimples
  • Constant itching, biting, clawing, or grooming

Help Your Pet Get Relief

This isn’t a one-and-done kind of thing. It’s a process.

Step 1: See your pet’s veterinarian. Don’t assume that because you can’t see any fleas, your dog or cat doesn’t have a flea allergy. Often, animals with one groom themselves constantly. They may remove any fleas from their bodies — but the allergic reaction from bites can last for weeks.

“If your dog or cat is scratching itself, get to a vet right away,” says Ari Zabell, DVM, a veterinarian and client advocate at Banfield Pet Hospital in Portland, OR. “Fleas and flea allergies are common, but it could also be another health problem, like a tick bite. It’s important to get the right diagnosis before your pet starts treatment.”

A vet will check your pet’s fur and skin thoroughly. They’ll check for fleas and “flea dirt,” which is flea poop that looks like pepper flakes. It often turns red when it’s wet. If the vet suspects another cause for your pet’s itching, they may order certain blood or skin tests to be sure. They’ll also make sure that your dog or cat doesn’t have any open wounds.

“If a pet is itching or chewing on itself a lot, bacteria or yeast can get into the skin and cause an infection,” says Elizabeth A. Layne, DVM, a clinical instructor of dermatology and allergy at the School of Veterinary Medicine at the University of Wisconsin-Madison.

Step 2: Break the cycle. Putting an end to your pet’s flea allergy means getting rid of fleas. Though they’re more common in warmer months, fleas can live year-round indoors. Once they lay eggs, new fleas hatch and then lay more eggs, which means your pet is constantly exposed.

“Using year-round treatment with a flea preventative medication can help break the cycle and prevent future allergic reactions,” Layne says.

Spot-on (or “topical”) medications and oral meds kill adult fleas. Some flea collars work well, too. Talk to your pet’s veterinarian about which treatment is best for your pet.

Medication is only half the battle. Fleas don’t actually live on animals. They live in carpets, bedding, and other surfaces in your home and jump onto your pet to eat. That’s why it’s important to wash your bedding, your pet’s bedding, and your throw rugs with detergent and warm water.

To remove fleas, flea eggs, and larvae, vacuum your carpets, larger rugs, and chair and sofa cushions. Empty the vacuum bag or canister afterward. Make sure to do it outside, or they could get back into your living space.

You may also consider using flea spray on your carpets and upholstered furniture. Be sure to keep your pets and your family away from sprayed areas until they’ve dried.

“Having fleas in your house doesn’t mean our home is dirty or you’re a bad pet owner,” Layne says. “Fleas are attracted to food sources, which is any cat or dog.”

Step 3: Ease the itch. Your pet’s veterinarian will recommend a topical, oral, or injected medication to ease your pet’s itching and inflammation. If your dog or cat has an infection, the veterinarian may also prescribe an antibiotic or antifungal medicine.

You may have heard that human antihistamines can treat pet allergies. Maybe, but probably not.

“The trouble is, they’re often not strong enough to ease inflammation for many pets with a flea allergy, and they don’t work at all for many animals,” Zabell says. “Talk to your vet before using them for your pet.”

At home, one of the easiest ways to help ease your dog or cat’s irritation is to give them a bath with cool water.

“Unless your pet hates water, this can help by making their skin feel better and removing some fleas,” Zabell says. 

Step 4: Avoid irritants. Don’t use flea shampoo or other topical flea products without talking to your pet’s veterinarian first.

“Flea shampoos and sprays can contain alcohol and other chemicals that can make a rash or wounds worse,” Layne says.

You may have seen onion or garlic tablets marketed for pet flea relief, but they can be toxic to dogs and cats. Skip essential oils and products that contain them, too.

“They can be very irritating to an animal’s skin, especially for a pet with a flea allergy,” Layne says.

Step 5: Stay in touch with your pet’s veterinarian. “Regular checkups are especially important for spotting infection and making sure your flea and allergy treatment plans are working,” Zabell says.

If you have a question between scheduled visits, don’t hesitate to call your vet.

“When it comes to your dog or cat’s health,” Zabell says, “it’s better to be safe than sorry.”

Show Sources


Ari Zabell, DVM, veterinarian and client advocate, Banfield Pet Hospital, Portland, OR.

Elizabeth A. Layne, DVM, clinical instructor of dermatology and allergy, University of Wisconsin-Madison School of Veterinary Medicine.

Carol Osborne, DVM, veterinarian, Chagrin Falls Veterinary Center, Chagrin Falls, OH; author, Naturally Healthy Dogs and Naturally Healthy Cats.  

Merck Manual: Veterinary Manual: “Flea Allergy Dermatitis.” 

Natural Resources Defense Council: “Nontoxic Ways to Protect Pets.” 

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