A guide to flea allergy dermatitis (FAD) in dogs

Itchy pup? If your dog has fleas and they seem exceptionally itchy, there’s a strong chance they’re suffering from flea allergy dermatitis (FAD). FAD is caused by hypersensitivity to a flea bite and the saliva injected by fleas during a bite.

FAD is one of the most common illnesses associated with flea infestation in dogs and cats and often includes itching, fur loss, and inflamed skin. A dog with FAD may suffer from just a few flea bites or even a single flea bite.

Clinical signs of FAD

The top signs of flea allergy dermatitis are itching, licking, and intense biting of the skin.   Other common signs look like:

• Small, raised lesions on the lower back, tail, head, and inner thighs
• Obvious restless and uncomfortable behavior
• Scratching, licking, rubbing, chewing, and even nibbling at the skin
• Hair may be stained brown from licking
• Sores or scabs and crusty, oozy skin
• Presence of fleas or “flea dirt” on the skin
• Unpleasant odor
• Hair loss

Generally, the areas affected include the rump and tail, hind legs as well as areas of the head. Pet owners will also see itching and hair loss in the region from the middle of the back to the tail and down the rear legs (also known as the “flea triangle”). Some dogs may even have visible bite marks on their skin.

👉 Just because you don’t see the fleas on your furry friend, it doesn’t mean they aren’t there. Fleas leave behind “flea dirt” or dark specs that look like black pepper. So if you don’t see fleas, this is a good sign to look out for.

Diagnosing flea allergy dermatitis in dogs

Vets will look for evidence of fleas or flea dirt on a dog’s skin when they examine the canine to determine if this parasite is the cause of the allergic response. In addition to inspecting more obvious signs of FAD, vets will also consider an intradermal test (ELISA) and skin biopsy to confirm.

Additionally, it’s common for a dog’s skin to develop a secondary infection with FAD. In these cases, a vet will use cytology to diagnose any other skin infections.

Your vet will typically collect a surface sample from a skin lesion using something simple like a piece of tape or pressing a microscope slide to the skin’s surface to gather matter for diagnostic skin tests.

Treatment for FAD

Fleas are becoming resistant to topical flea and tick preventatives, such as Frontline, Advantix, and Effitix. Therefore, most vets will recommend an oral treatment product, like Bravecto.

Your veterinarian will discuss the pros and cons of the various treatments for FAD with you during the examination and will recommend the safest and most effective treatment for your pet’s needs.

👉 Whenever you give something new to your dog, watch them closely for 24-48 hours. Call your vet if you notice any hives, vomiting, or diarrhea.

Tips for preventing fleas

Prevention is a big part of effective treatment for FAD. Here are a few tips to help!

• Add extra repellent products. Some topical flea/tick products may provide some repellent qualities whereas oral products can’t. Your vet may recommend putting them on a comprehensive oral medication, along with a flea-repellent collar like Seresto for extra protection.
• Flea shampoos aren’t effective. Flea shampoos may kill adult fleas, but they won’t stop eggs from hatching, so these aren’t considered an effective method for treating fleas on your pet.
• Don’t stop administering. Once a flea infestation is eradicated, most pet owners stop administering flea products. Instead, all pet owners need to talk to their vet about a monthly flea control medication year-round.
• Treat all pets in the home. Also, it’s important for all pets (dogs and cats) in the household to be on flea prevention. Talk to your vet about flea preventatives for cats as they are different from dogs.

If you notice your dog itching, licking, or excessively biting at their skin, this may be an indicator your dog has FAD. Pay attention to other warning signs like skin lesions, scabs, and loss of hair, and take your pup to the vet for a professional diagnosis and treatment.

Frequently asked questions

How do you treat flea allergy dermatitis?

Since the injection of flea saliva causes the allergic response associated with FAD, it’s important to get to the root of the cause for treatment and prevent fleas from biting your dog. Even if you don’t see fleas on your dog, consistent flea control is essential for treating and preventing FAD. After eradicating fleas with an oral treatment, you’ll need to treat the skin irritation.

In mild cases, Benadryl can provide some relief. However, most dogs with FAD need more help beyond over-the-counter medication. Talk to your veterinarian about the need for steroids or other allergy meds such as Apoquel or Cytopoint.

How long does flea dermatitis last?

Once fleas are controlled it can take up to two weeks after a bite for your dog to stop itching. If a rash has developed on your pet’s skin or they have raw, irritated, or bleeding areas on their body, it can take significantly more time for those lesions to heal.

Can you have flea allergy dermatitis but no fleas?

The absence of live fleas doesn’t rule out FAD. A dog can experience FAD with a single bite, depending on how sensitive their skin is to a flea’s saliva. Some dogs experience a more adverse reaction than others.

Is flea allergy dermatitis an emergency?

Flea allergy dermatitis is not a life-threatening emergency. However, it is extremely uncomfortable for dogs. Severely itchy dogs often show signs of distress and are unable to sleep well or get comfortable. If you notice signs of FAD, be sure to get your dog to a veterinarian as soon as possible for treatment.

What does flea dermatitis look like?

If your dog has flea allergy dermatitis, their skin will appear red, be mild to severely itchy, and may have bumps, crusts, or lesions.