Flea Allergy Dermatitis in Dogs: Everything a Pet Parent Needs to Know

Are you tired of waking up in the middle of the night to your dog’s constant scratching?  

Are you worried about your dog’s well-being and fearful you’ll have a flea infestation? Well, there’s a good chance they probably have flea allergy dermatitis (FAD).  

Read on to learn more about this condition, how vets diagnose it, and the treatment options that can restore a night of peaceful sleep for both of you and improve your dog’s quality of life.  

What Is Flea Allergy Dermatitis in Dogs?

Fleas are blood-sucking parasites that limit a dog’s quality of life and can also harbor other infectious diseases such as plague, tularemia, and tapeworms.  

As fleas bite a dog and drink a blood meal they put their saliva into the dog, and that triggers an immune response. Over time, this immune response can become exaggerated, leading dogs to want to bite, scratch, and chew at themselves. Secondary skin infections often occur, which may show up as hair loss, reddened skin, crusts, and scaling.  

Flea allergy dermatitis is a major cause of concern for pet parents and is the most common condition affecting the skin, especially in more temperate climates like those in the southern and southeastern United States.  

Dogs with FAD are sensitive to even a few flea bites, and even if you don’t see any actual fleas on your dog, they may still have this condition.  

FAD is not considered a medical emergency, but it shouldn’t be overlooked. Continual itching and scratching and secondary skin infections affect your dog’s well-being and can negatively affect the human-animal bond and the entire family.  

Symptoms of Flea Allergy Dermatitis in Dogs

Symptoms of flea allergy dermatitis in dogs vary in intensity and can worsen over time. Typically, you will notice:  

• Hair loss, often over the rear end and base of tail 

• Itching and scratching 

• Crusts 

• Redness to the skin 

• Presence of fleas or flea dirt (flea feces, partially digested blood) 

• Anemia and lethargy, when there are huge infestations  

Causes of Flea Allergy Dermatitis in Dogs

Flea allergy dermatitis is an allergy, more specifically, a hypersensitivity reaction against the proteins in the flea’s saliva. The dog’s immune system causes an inflammatory reaction, leading to intense itching and scratching.  

Because it is an allergy, not all dogs are affected, and even in multi-pet homes, some dogs may react more severely to fleas than others.  

Any age, breed, and sex can be affected by flea allergy dermatitis, but this condition is more commonly seen in dogs 5 years and younger.  

How Veterinarians Diagnose Flea Allergy Dermatitis in Dogs

A physical exam showing the above symptoms and finding fleas or flea dirt (often seen through use of a flea comb) is often enough to diagnose the condition—or at least to highly suspect FAD.  

However, because other skin diseases have similar symptoms, your veterinarian may recommend tests to help confirm the diagnosis, such as: 

• A skin impression, to look for signs of bacteria or yeast infections 

• Skin scraping, to look for evidence of parasitic mites 

• Fungal culture +/- PCR, to diagnose ringworm infections 

Your vet may even use a positive response to therapy (noting that treatment works) to confirm the diagnosis. 

More advanced tests like intradermal skin testing with a dermatologist are often not needed, but they may be recommended for your dog. 

Treatment of Flea Allergy Dermatitis in Dogs

Treatment for dogs with flea allergy dermatitis is twofold: 

1. Treat the fleas 

2. Treat the symptoms 

Flea control is the most important aspect of treatment, and fortunately there are multiple effective products readily available for purchase and application.  

Products are either placed topically on your dog’s skin (Frontline Plus), worn as a collar around the neck (Seresto), or given monthly or every three months as a pill (Simparica and Bravecto, respectively). Be sure to consult your veterinarian on the safest product for your pet.  

The environment must also be treated. Vacuuming weekly—especially under the sofas and refrigerator and in corners—is important, along with throwing out your pet’s bedding or washing it in warm soapy water.  

Talk to a pest control agency about spraying the yard with people- and pet-safe chemicals.  

Diatomaceous earth or Knockout sprays can be used in the home, but be careful to follow the instructions exactly. These products should never be put on your pet. 

Anti-itch medications, either in an oral tablet or injection, are also important for symptomatic relief. Steroids (such as prednisone or dexamethasone), Apoquel, Cytopoint, and antihistamines like hydroxyzine are often prescribed.  

If FAD is not caught early, dogs can get a secondary skin infection and may need more treatment, including oral antibiotics such as cephalexin, Simplicef, or Clavamox.  

Topical ointments, shampoos, or conditioners with antimicrobials, antifungals, and steroids may be needed to help treat the infection and ease inflammation (swelling) and discomfort.  

Some examples include:  

• Pet MD Medicated Shampoo  

• KetoChlor  

• Duoxo S3 

• Animax  

Recovery and Management of Flea Allergy Dermatitis in Dogs

The flea life cycle is on average about three weeks, but the pupa stage can stay in the environment for months, ready to hatch at the right moment. Thus, when fleas are on your dog, you can expect treatment to last anywhere from three weeks to about three months.  

Dogs can recover and symptoms typically will improve within a few days of treatment. Certain products such as Capstar start killing fleas within 30 minutes. A recovery cone may be needed at first to prevent self-trauma from biting and chewing.  

Your veterinarian may also recommend a flea repellent like Vectra 3D along with regular flea control to minimize the chance of flea bites altogether.  

Prevention of Flea Allergy Dermatitis in Dogs

Monthly year-round flea control is recommended for all pets. Flea control is often more cost-effective, easier to give, and more time-efficient. 

 Make sure that all pets keep up with flea control so fleas don’t get shared. In the home and yard:  

• Remove yard debris, such as leaf litter 

• Keep the lawn mowed regularly  

• Prevent access to wildlife 

• Concentrate outdoor pest sprays on shaded areas, under the porch, or under trees and bushes 

• Vacuum regularly and wash your pet’s bedding