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Dog scratching themself due to flea allergy
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  • Some dogs are hypersensitive to flea bites and will experience a much more severe reaction.
  • Flea allergy in dogs can be quickly diagnosed by seeing fleas or flea dirt in a dog's coat and noticing that they are chewing or scratching themselves more often.
  • If diagnosed, a flea control product will be needed for all pets in the house.
  • Thankfully, flea allergy dermatitis is easily preventable and begins with strict, year-round flea control.

Fleas. Just saying the word is enough to make anybody’s skin crawl. We often think of fleas being in unclean environments or on dirty animals, but the truth is that fleas are all over the place, including our backyards, porches and sometimes even in our clean homes. 

Fleas are still so prevalent that flea allergy dermatitis (FAD), or itching due to fleas, remains the number one cause of itching and allergic skin disease in dogs in the United States. 

Flea allergy dermatitis can be frustrating for pet owners, extremely uncomfortable for dogs and fleas can transmit disease to animals and humans. Fortunately, flea allergy dermatitis is easily preventable with a monthly preventative, like Simparica TRIO, and treatable. Here’s what you need to know about this common canine affliction.

Can Dogs Be Allergic to Fleas?

Dog looking sad leaning over corner of couch

The majority of dogs will find flea bites uncomfortable. However, some dogs are hypersensitive to flea bites. These pets will experience a much more severe reaction to flea bites than other dogs and are therefore considered allergic to fleas. 

Dogs with flea allergy dermatitis, also referred to as flea bite hypersensitivity, have often been already diagnosed with other allergies such as food or environmental allergies. Flea allergies can develop at any age, but most cases of FAD appear in dogs between 2 to 5 years old. Flea allergies are the most common type of allergy diagnosed in dogs and cats.

What Causes Flea Allergy in Dogs?

Dog scratching from having fleas on fur

Flea allergies occur once an animal has been exposed to fleas. As a flea feeds, it releases saliva rich in enzymes, peptides, amino acids and histamines. The body recognizes these compounds as antigens, triggering an immune response. 

Some dogs may show signs of itching within minutes of a bite, while others may experience a more delayed reaction 24 to 48 hours later. A single flea bite can make a sensitive pet itchy for up to two weeks. 

In many cases of flea allergy dermatitis, dog owners are confused about their pet’s symptoms because they have not seen a flea on their pet. However, it is important to acknowledge that fleas are tiny, about the size of a sesame seed, and very fast. Fleas can discreetly hop on and off your pet while they are on a walk or playing in the park. Fleas also do not need to live on your dog. These tiny, mighty bugs can live in your home, hiding in the cracks between cushions or in your dog’s bed after biting your dog. Another reason owners may not always find fleas on their pet is that they may be biting and scratching so vigorously that the fleas are removed before they are spotted. 

Dog Flea Allergy Symptoms

Dog biting leg from having flea allergy reaction

Dogs suffering from flea allergy dermatitis often display the following symptoms:

  • Itching, redness, and crusting primarily on their back from just behind the rib cage to the base of the tail (this area is often referred to as the flea triangle.) 
  • Biting or chewing their skin excessively
  • Raw open wounds where hair has been chewed called hot spots around the base of the tail or the face
  • Dragging themselves along the carpet
  • Hair loss secondary to biting, chewing, or scratching
  • Red bumps on the skin similar to pimples
  • Oily appearance to the skin and coat
  • Small black dots, called flea dirt, in the coat
  • Loss of sleep/scratching through the night
  • Decreased appetite and restlessness

Some of these symptoms occur because dogs are itching so severely that they traumatize their skin barrier and allow secondary infections to form. These infections compound a pet’s itch and irritation, making the situation even more uncomfortable for affected dogs. 

Diagnosing Flea Allergy in Dogs

Dog scratching because of fleas on fur

Flea allergy in dogs can be quickly diagnosed by discovering fleas or flea dirt (little black specks of dried blood) in a dog’s coat. That said, the absence of fleas does not exclude flea allergy dermatitis as the cause of a dog’s itch because, as we discussed, fleas are not always present on a dog after they have taken a meal and caused the allergic reaction. 

In many cases, FAD is diagnosed based on the symptoms, coupled with the lack of consistent, reliable flea prevention being administered year-round.

Your veterinarian will need to perform a physical exam to rule out other causes of itching and make sure your dog hasn’t developed any secondary skin infections due to the severity of their itching.  

Dog Flea Allergy Dermatitis Treatment

Dog being shampooed with flea shampoo

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First and foremost, any fleas on the pet will need to be completely removed, and new bites must be prevented. Your veterinarian will prescribe a reliable and safe flea product to kill any fleas actively on your pet and ensure they’re protected against future infestations, such as Simparica TRIO, Revolution, or NexGard PLUS.

A flea control product will be needed for all pets in the house (cats included) to eradicate these pesky insects from the animal’s environment fully. 

An anti-itch medication may also be prescribed to help your pet feel more comfortable while their skin heals. This may be a steroid or a prescription allergy medication such as Apoquel or Cytopoint. Apoquel is an oral tablet for dogs that relieves and controls allergic itch and inflammation due to skin allergies. Cytopoint is an injection given at your veterinarian’s office that controls allergic itch in dogs and provides relief for up to 8 weeks.

Apoquel medication bottle

Secondary skin infections that may have developed will also need to be treated. Typically this will be a medicated shampoo and possibly oral antibiotics or antifungals as deemed necessary based on physical exam findings. 

Environmental treatment is also necessary. The inside of the house should be treated using a combination of flea bombs, sprays, vacuuming carpets and couches, washing all upholstery such as bedding, curtains, throw blankets and more. Treating your backyard, patio and porch is also advisable. In some cases, such as for large homes or those with many animals, hiring professional exterminators is a good idea.

Treating the environment alone is not sufficient to prevent FAD, as it will only rid the home and surrounding area of fleas present at that moment. In a short time, new fleas can move in and take root, especially if there are unprotected pets in the home to provide hungry fleas with meals.

Preventing Flea Allergy in Dogs

Dog getting flea treatment to neck

Thankfully, flea allergy dermatitis is easily preventable and begins with consistent, year-round flea control. Monthly flea prevention comes in topical and oral forms to fit a variety of pets’ lifestyles and needs. For example, Revolution topical solution is easy to apply to your dog’s skin once a month and protects against fleas as well as American dog ticks, ear mites, sarcoptic mange, and heartworm disease. Simparica TRIO is a flavored chewable tablet you give your dog monthly to prevent fleas, ticks, and heartworm disease, while fighting dangerous intestinal parasites, including roundworms and hookworms.

Other products, such as flea control collars, are beneficial if applied correctly and changed regularly. 

Unfortunately, many over-the-counter options are not reliable at eliminating fleas entirely, so a prescription flea control product is necessary for pets who are hypersensitive to flea bites. NexGard PLUS is only available by prescription, so ask your veterinarian if it’s a good fit for your canine companion.

Despite popular belief, fleas are not entirely dormant in winter months, especially if they have found their way inside our temperature-controlled homes. Therefore, flea products should be given year-round. If flea control products are discontinued in the winter months, it can be much harder to prevent an infestation in the spring and summer when flea numbers are the highest.

Unfortunately, fleas are here to stay, no matter how clean we keep our pets and our homes. By keeping our pets on a reliable and safe flea control product year-round, dog owners can avoid unnecessary veterinary visits, expensive treatments and save their dog from the discomfort that flea bites can cause.