Flea Allergy Dermatitis in Cats

Mindy Joyner, DVM
By Mindy Joyner, DVM on Mar. 14, 2022
Cute Siberian Cat

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What Is Flea Allergy Dermatitis in Cats?

Flea allergy dermatitis is a common skin allergy in cats that can occur from a flea bite. Cats can be allergic to the flea’s saliva, which causes the release of a histamine-like compound, resulting in a very itchy skin condition. Flea allergy dermatitis commonly occurs on the head, neck, and back (also known as the “racing stripe” pattern on the skin).  

Allergies are caused by a prior exposure to an allergen. If the body’s immune system recognizes the substance as “foreign,” a reaction may occur. One flea bite can be enough to make your cat’s skin itchy for up to 2 weeks.  

Cats may also be allergic to environmental allergens (pollens, dust, mold, and dander) or have food allergies (specifically to the chicken and fish protein sources in most commercial diets). Flea allergy dermatitis differs from food and environmental allergies based on the pattern of skin lesions and the history of the pet.

Symptoms of Flea Allergy Dermatitis in Cats

If your cat has flea allergy dermatitis, their skin will appear red (erythema), be mildly to severely itchy (pruritus), and may have crusts or small bumps (papules). Most pet parents notice their cat scratching frequently and excessively grooming. You may also notice hair loss on the head, neck, or back (it can also occur on the abdomen and inner thighs). Any itching and hair loss in these locations is suggestive of flea allergy dermatitis.

Causes of Flea Allergy Dermatitis in Cats

Cats can be allergic to the saliva of the fleas, which is transferred during the flea bite. Fleas use a mouthpart called a proboscis to suck blood rather than biting. Once the saliva is transferred, a histamine-like compound, along with other inflammatory mediators in the skin, causes the noticeable symptoms of skin redness and itching. One flea bite is enough to cause a reaction in an allergic cat.

How Veterinarians Diagnose Flea Allergy Dermatitis in Cats

Flea allergy dermatitis is diagnosed during a physical exam by your veterinarian, with or without your cat having a history of fleas. No other tests are needed to confirm this diagnosis.  

Live fleas may be seen, but the absence of live fleas doesn’t rule out this condition. Fleas can jump on your cat, bite, and jump off. Or your cat may bite or lick at the area of the flea bite and remove the flea.  

A flea comb may be used to look for live fleas or evidence of fleas (flea feces). Flea feces will look like flecks of pepper on the hair, coat, and skin, and they are often misinterpreted by pet parents as dirt. Skin lesions (bumps or hair loss) along with itchy skin located at the base of the tail is sufficient evidence to make a presumptive diagnosis of flea allergy.

Treatment of Flea Allergy Dermatitis in Cats

The goal of treatment is to alleviate the itching and treat for fleas on the cat as well as in the environment. For mild itching, over-the-counter topical sprays that have hydrocortisone can be used for several days to help control itching. This spray should not be used on the head or face because it could damage the cat’s eyes.  

An Elizabethan collar (also known as an e-collar or cone) can be used to help prevent scratching on the head and neck.  

Treatment of Itching 

Prescription medications such as corticosteroids are often necessary if itching is moderate or severe. These medications include an oral tablet such as prednisolone or an injectable form such as methylprednisolone acetate (also known by brand name Depo-Medrol). Injectable forms can be a good option for pet parents since most cats are not easy to medicate daily with a tablet.  

Moderate to severe scratching may lead to a skin infection. Small, raised, pinkish red bumps or pimples can occur, as well as ulceration of the skin (sores) and scabs from severe scratching. Skin infections will need to be treated with antibiotics, which your veterinarian can prescribe. These are available in oral or injectable form.  

Recovery and Management of Flea Allergy Dermatitis in Cats

Cats will recover once the fleas are controlled. Itching may take 1-2 weeks to resolve completely.  

Prevention of Flea Allergy Dermatitis in Cats 

Flea control is essential. Cats with flea allergy dermatitis are very sensitive to even a few flea bites. Indoor and outdoor cats are both susceptible to fleas since they can be anywhere in the environment. For this reason, flea control is recommended for all cats in the household all year round. Fleas survive very well in winter months in most states in the USA.  

The spot-on and oral products listed below are the most effective flea control. Shampoos and powders are much less effective and can cause further skin irritation. Consult your veterinarian before using any flea control products. Some products that are safe for dogs are toxic to cats. Do not use permethrin-containing products in cats. Your cat’s age and weight will matter when choosing flea products.  

Recommended over-the-counter flea control products (available without a prescription) include: 

  • Topicals: Frontline, Advantage II, Effipro Plus, Cheristin (each effective for 30 days) 

  • Collar: Seresto (effective for 8 months) 

  • Oral: Capstar (as needed, can be given daily; treats live flea infestation, but will not prevent fleas) 

Prescription products that have proven more effective include: 

  • Topicals: Revolution (effective for 30 days; also prevents heartworm and intestinal parasites), Bravecto (effective for 90 days) 

  • Oral: Credelio (effective for 30 days) 

The environment the cat lives in should also be treated, both indoors and outdoors. If you treat the cat and not the environment the cat lives in, the flea life cycle will continue and the fleas will return. Your veterinarian can offer suggestions for products that are safe for pets indoors. Keep in mind that to control the entire flea life cycle, the product should contain an insect growth regulator (known as an IGR) to kill the flea eggs and larvae that can hatch and become adult fleas. You may need to have the indoor and outdoor areas treated professionally by pest specialists.  

Flea Allergy Dermatitis in Cats FAQs

How long does flea allergy dermatitis in cats last?

The itching can last for days to weeks. The skin irritation will resolve sooner if the fleas are controlled.

Are flea allergy dermatitis home remedies available?

Bathing your cat in cool or lukewarm water or with mild oatmeal shampoo may help soothe the skin. If your cat’s skin is ulcerated or has scratches, it is best not to bathe them. Over-the-counter topical 1% hydrocortisone sprays for pets are available and can be used for minor relief from itching until you can see your vet.

Is flea allergy dermatitis contagious to humans?

No, flea allergy dermatitis is not contagious to people. However, if fleas are present on household pets, humans may be more susceptible to them and other diseases they can spread.

Is flea allergy dermatitis contagious to other pets?

The dermatitis is not contagious to other pets. But the fleas will be happy to spread by jumping on another host, such as other pets in the household.

Featured Image: iStock.com/vitapix

Mindy Joyner, DVM


Mindy Joyner, DVM


Dr. Mindy Joyner received her Bachelor of Science in Animal Science from North Carolina State University. She studied ruminant nutrition...

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