Flea Allergy Dermatitis in Cats – Symptoms & Treatment

What is flea allergy dermatitis?   Causes   Symptoms   Diagnosis   Treatment   Prevention

Flea allergy dermatitis in cats
Image Nottingham Vet School, Flickr

What is flea allergy dermatitis?

Flea allergy dermatitis is a common itchy skin disease that is caused by a hypersensitivity to the proteins in the saliva of the flea which is injected into your cat’s skin when the flea feeds.

There is no breed or sex predisposition to flea allergy dermatitis although it is less common for cats under 1 year old to have flea allergy dermatitis.

Flea allergy dermatitis is one of the major causes of miliary dermatitis in cats and is the most common allergy seen in cats as well as being the most common skin disease to affect cats.

Fleas can be active year-round in warmer climates, or in the summer months in cooler areas. Numbers tend to peak towards the end of summer and into early autumn.


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

Flea allergy dermatitis is one of the major causes of miliary dermatitis in cats and is the most common allergy seen in cats as well as being the most common skin disease to affect cats.


Flea allergy dermatitis in cats

Symptoms vary depending on the degree of sensitivity. Common symptoms include:

  • Raised crusty bumps (papules) or scabs on the skin (miliary dermatitis), this most commonly affects the back, particularly the area closest to the base of the cat’s tail and the neck.
  • Frequent scratching, licking and biting of the fur, especially around the neck, on the back and the base of their tail.
  • Self-trauma from scratching can lead to open sores, particularly around the neck.
  • Thinning fur in the affected area from over-grooming.
  • Severe scratching can damage the skin and lead to secondary bacterial infection. 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 your 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

Your veterinarian will perform a physical examination of your cat and obtain a medical history from you. Diagnosis is usually made during examination by the presence of miliary dermatitis around the back and base of the tail and often sores around the neck.

He may also notice fleas and/or flea dirt in your cat’s coat. It should be noted though that just one bite is enough to trigger a hypersensitivity and in some cases, no fleas will be found on your cat because he is so efficient at removing them during grooming. This is particularly common in extremely sensitive cats who groom excessively.

Sometimes a piece of white paper will be placed underneath your cat while his fur is gently roughed up. The paper is then sprayed with water, and if any flea dirt is present, it will dissolve, leaving a reddish appearance.

As there are many other causes of miliary dermatitis in cats, your 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.


Treatment involves several modalities including killing the fleas on your cat and in the home and relieving symptoms associated with a flea allergy.

  • The only permanent solution for flea allergy dermatitis is to completely eliminate fleas from your cat and the environment. As well as that, preventing re-infestation of fleas by regular flea treatment. This involves a two-pronged approach. Treating your cat and treating the environment (including your cat’s bedding). Treat all household pets for fleas at the same time.
  • Treating secondary skin infections caused by excessive biting and scratching of the skin. This may involve a course of antibiotics, medicated shampoo and or a topical medication.
  • Antihistamines or oral tablets or steroid injections to control inflammation and reduce itching. Long-term steroid use can produce side effects, therefore the dosage should be as small as possible and treatment limited until your cat has healed and the flea problem has been controlled.
  • Anti-inflammatory injection to reduce the itching.
  • Hyposensitization (desensitisation). This involves injecting minute amounts of flea antigen into the cat in the hope that it will re-programme the immune system so it’s not hypersensitive to flea antigen.  Treatment has shown limited success, unfortunately.
  • Antibiotics to treat a secondary bacterial infection.
  • If your cat has been diagnosed with flea allergy dermatitis, he should be treated for tapeworm as ingestion of fleas during grooming can transmit the parasite.


Strict flea control is the best way to avoid/limit your cat’s exposure to fleas and therefore flea bite allergy. There is a range of flea products on the market. Flea collars are not as effective as the newer topical flea products or oral tablets to controlling fleas.  Some flea products are becoming less effective as fleas build up a resistance. Your veterinarian is the best person to speak to in regards to flea control products.

Flea control safety:

  • If you are using a topical flea product, avoid shampooing your cat afterward as this can wash off the product.
  • Don’t mix flea control products unless your veterinarian recommends it. This can lead to a doubling up of the active ingredients and 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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