Flea Allergy Dermatitis in Cats – Symptoms & Treatment

Flea Allergy Dermatitis in Cats – Symptoms & Treatment


What is flea allergy dermatitis?   Causes   Symptoms   Diagnosis   Treatment   Prevention

Flea allergy dermatitis in cats

Flea allergy dermatitis at a glance

About: Flea allergy dermatitis is a hypersensitive reaction to proteins in flea saliva which it injects into the skin when it feeds.


  • Intense itching
  • Small, raised, hard bumps, especially along the spine of the cat and around the neck (miliary dermatitis)
  • Hair loss
  • Excessive grooming
  • Secondary bacterial can develop due to self-trauma

Treatment: Diligent flea control on all pets as well as treat the home for fleas with a pet-safe insecticide. Other therapies can include antibiotics, antihistamines and steroids.

Also known as: Flea bite hypersensitivity, FAD


What is flea allergy dermatitis?

Flea allergy dermatitis in cats

Flea allergy dermatitis (FAD) is a common itchy skin disease caused by a hypersensitivity to components of the flea saliva (antigens, amino acids, aromatic compounds, polypeptides, and phosphorus), which the flea injects into the skin as it feeds.

FAD is a significant cause of miliary dermatitis in cats as well as the most common type of allergy seen in cats and the most common skin disease to affect cats.

Fleas can be active year-round in southern parts of the globe or the summer months in northern regions. Numbers generally peak towards the end of summer and into early autumn.

There is no breed or sex predisposition to flea allergy dermatitis although it is less common for cats under one year old to have flea allergy dermatitis.


There are 15 known allergens in flea saliva, each one is capable of causing an allergic reaction in the cat, and just one bite is enough to trigger an allergic reaction.


Flea allergy dermatitis

  • Raised crusty bumps (miliary dermatitis) on the skin, common areas include the face, neck and back (near the base of the tail).
  • Frequent scratching, licking and biting.
  • Self-trauma leads to open sores, particularly around the neck.
  • Areas of hair loss (alopecia).
  • Secondary bacterial infection can develop due to trauma. This may present as red and inflamed areas along with an unpleasant odour coming from the skin.
  • The presence of fleas or flea dirt (feces). Flea dirt is reddish black, with a similar appearance to a grain of pepper. Fleas and flea feces are easier to spot on light coloured cats.
  • Examination of the cat’s bedding may reveal flea feces and eggs, which have a salt and pepper appearance.


Flea allergy dermatitis in cats
Image Nottingham Vet School, Flickr

The veterinarian will perform a physical examination of your cat and obtain a medical history from you. In most cases, the veterinarian will be able to diagnose FAD based on clinical symptoms alone.

Fleas and/or flea dirt may be present in the cat’s coat; however, just one bite is enough to trigger a hypersensitivity, and in many cases, no fleas will be found because cats, especially those with FAD are such efficient groomers.

As there are many other causes of miliary dermatitis in cats, the veterinarian may also recommend skin patch testing (or intradermal testing). This involves shaving an area of skin and injecting the area with small amounts of common allergens to see if your cat mounts an allergic response to any.

Specialised blood tests can also confirm flea allergy dermatitis by detecting IgE antibodies in the blood.


Flea allergy dermatitis in cats
Image Nottingham Vet School, Flickr

The only permanent solution for flea allergy dermatitis is to eliminate fleas and prevent re-infestation of fleas with a regular flea treatment regime.

  • Treat the cat with a veterinary-approved adulticide flea spray, spot-on solutions or tablets.
  • As the majority of the flea life-cycle is spent in the home, it is vital to treat the home with insect growth regulators (IGR’s) which includes beds, toys, rugs, carpets, and outdoor areas
  • Antibiotics or medicated shampoos to treat secondary skin (pyoderma) infection.
  • Oral glucocorticoid therapy (usually prednisolone) to control inflammation and relieve itchiness. Long-term steroid use can produce side effects, therefore will be discontinued once symptoms resolve.


Strict flea control to prevent a flea infestation in the first place. Veterinary approved flea products are the most effective. These include topical treatments and oral tablets. Some flea products are becoming less effective as fleas build up a resistance.


  • If you are using a topical flea product, do not shampoo the cat afterwards as this can wash off the topical treatment.
  • Don’t mix flea control products unless your veterinarian recommends you do so, to avoid doubling up of products which can cause toxicity.
  • Never use a flea product designed for dogs on your cat. Dog flea products contain different ingredients which are highly toxic to cats.

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