Flea Allergy Dermatitis: Pictures, Signs & Treatment

For us pet people, autumn is a special time.  It’s a whole genre of senses, activities and destinations all shared with our pets! It’s snuggling with your cat on the sofa while the late-season sun streams in.  It’s crunching through the leaves in the crisp air with your dog. It’s also the time of year when that idyllic mood is most likely to be disturbed by the scratching, licking, head-shaking discomfort of an itchy pet.


Fleas are external parasites that can make their homes on dogs, cats and even wildlife. They live on the body of your pet and lay eggs, which fall onto carpets, bedding and grass all around your home.  After the eggs mature, they turn into larvae, then into a new generation of fleas. Flea populations reach their peak in the late summer and early fall. While insects themselves can be a nuisance for your pet, it’s your animal’s own immune reaction to flea bites that can really make them miserable.

What is Flea Allergy Dermatitis?

Flea allergy dermatitis is very common. It occurs when a dog or cat develops a strong immune response to compounds found in flea saliva. So, when a flea bites a small area, the whole body responds. The pet can become extremely itchy, developing skin inflammation and lesions just about anywhere.

Signs of Flea Allergy Dermatitis

This immune-driven condition is more than just a matter of having fleas. Non-allergic dogs and cats can tolerate a small population of fleas with little more than an occasional scratch. Pets with flea allergy dermatitis have severe itching and additional clinical signs that may need veterinary attention. These signs can include:


  • Moderate to severe itching (scratching, licking, chewing)
  • Crusting lesions on the lower back, base of the tail, and on the inside and backs of the thighs
  • Hair loss
  • Darkening or thickening of the skin
  • Skin infections
  • Red or raw skin
  • Presence of fleas or flea excrement (flea dirt)


  • Moderate to severe itching (scratching, licking, chewing)
  • Thickened or crusting lesions on the face, neck, and back
  • Hair loss, especially around the face and along the spine
  • Small crusts throughout the coat
  • Skin infections
  • Red or raw skin
  • Presence of fleas or flea excrement (flea dirt)

Examples of flea allergy dermatitis: 

A dog with lesions on its back from flea allergy dermatitis (source: The Veterinary Nurse)

A cat with hair loss and raw skins above its eye from flea allergy dermatitis (source: pdsa)

How is Flea Allergy Dermatitis Diagnosed?

Your veterinarian will ask you questions about your pet’s general health to understand what has changed. They’ll ask about your pet’s symptoms, when they started and what your regular flea control program is. During a complete physical examination, they’ll probably pay extra attention to your pet’s skin and coat. When fleas or flea dirt are present in combination with any skin lesions, flea allergy dermatitis will become one of the lead suspects for causing your pet’s problem. Your vet may even recommend skin or blood allergy tests to zero in on the diagnosis.

How is Flea Allergy Dermatitis Treated?

Flea control and prevention could involve medication for all pets in the home, as well as treatment for your home or yard. Flea meds come in a variety of forms, including pills, chewable medicated treats and topical drops. Your vet may also recommend using a spray or powder to kill fleas and larvae living on the ground. Your climate, the details of your pet’s home, personality and health should be considered when determining the best flea control program.

A good flea control program has three main components:

  • The ability to kill adult fleas
  • The ability to block eggs and larvae from maturing
  • Residual activity – the ability to remain effective for several weeks between treatments

Flea prevention and control are often needed year-round for pets with flea allergy dermatitis. Your veterinarian can help you choose a safe and effective flea control program for your pet. Symptoms of flea allergy dermatitis may persist for a few weeks after fleas are effectively controlled. Pets with severe itching or skin lesions may require additional medical care on top of flea control. This could include soothing topical preparations, anti-itch or anti-inflammatory medications and sometimes antibiotics.

Home Remedies and Over-the-Counter Solutions

Unfortunately, most natural, or over-the-counter products for flea control don’t meet the criteria listed above and they’re likely to leave your pet vulnerable to flea bites that could trigger weeks’ worth of skin reactions. It’s best to seek your veterinarian’s advice to get the best flea control for your pet’s situation.

On the bright side, there are many natural options for soothing your pet’s itchy skin that can be used in combination with prescription flea control:

  • Essential fatty acids – found in fish and flax oil, this nutrient can soothe inflammation and itching when given topically or orally.
  • Colloidal oatmeal – baths, conditioners and leave-on products for pets can help calm itchy skin.
  • Cool water – a cool bath can temporarily provide relief to irritated skin and is a great before-bed routine. Just ensure complete drying, and don’t bathe your pet too soon after using topical flea products.
  • Calendula – this herbal remedy can be found in pet-safe ointments, tinctures, and sprays to alleviate itching and speed wound healing.

Flea allergy dermatitis is extremely common and can affect any dog or cat.  Before your pet starts to show signs of flea allergies, enroll them in an insurance plan to help manage the cost of veterinary care.

Written by:
Dr. Sperry, DVM, Veterinary Advisor, Pets Plus Us
The information provided and contained herein are the opinions of PTZ Insurance Services Ltd. which are based on external publication. The content is not intended to be a substitute for professional veterinary advice. PTZ Insurance Services Ltd. assumes no responsibility or liability for any loss, claims or damages arising out of the within content.