Flea Allergy Dermatitis (FAD) in Cats

What Causes Flea Allergy Dermatitis?

When a flea bites your cat, some of the flea’s saliva gets into the bite wound. Most cats are not allergic to flea saliva and can be bitten by fleas without any symptoms.

However, many cats are allergic to proteins, called antigens, in the saliva of the flea. If your cat is allergic, their immune system releases substances that make your cat feel itchy. Just one flea bite can cause your cat to become itchy, and that inflammation and itchiness can last for a few weeks.

Symptoms of Flea Allergy Dermatitis in Cats

Cats of any age, sex, or breed can get FAD. Many cats will try to relive their itch by licking and scratching at their skin. Other cats are more secretive, and you don’t see them scratching, but you may start to see the evidence of this in their skin and fur. The most commonly affected areas are the back ⅓ of the body and the back of the neck or head.

Common symptoms of FAD include:

• Symmetrical hair loss due to excessive licking.
• Miliary dermatitis. This is a term for small, scab-like sores on the skin of cats. Since cats tend to have a thick coat of fur, you may not initially see the scabs, but you can feel them when petting your cat.
• Excessive scratching and licking.
• Severe self-trauma. Cats may scratch their skin enough to cause open wounds or sores.
• Seeing fleas on your cat. We often only see fleas in severe flea infestations. Common places to find them include the belly, back, or near their tail.
• Lip ulcers. These ulcers are associated with a condition called eosinophilic granuloma complex.

Diagnosing Flea Allergy Dermatitis in Cats

Surprisingly, we don’t often diagnose FAD by finding fleas. This is because cats are really good at finding and removing fleas from their body. Also, cats do not need to be infested with fleas to have this reaction. A bite from just one flea can cause FAD.

To diagnose FAD, we start by looking for fleas, or evidence of fleas, called “flea dirt”. “Flea dirt” is actually flea poop, and it looks like black bits of dirt. It turns reddish brown when put on wet paper, as it contains digested blood. Intradermal allergy testing can also identify flea allergy, although this is more commonly done by a veterinary dermatologist.

Other causes of skin diseases in pets that must be ruled out include atopic dermatitis, food allergy dermatitis, sarcoptic or demodectic mange, other skin parasites, and bacterial folliculitis.

In many cases, we diagnose FAD by a response to treatment. If their symptoms resolve after treating your pet and the environment for fleas, it is most likely that FAD was the cause of the skin issues.

Treating Flea Allergy Dermatitis in Cats

The best way to treat FAD is to control fleas. We do this with flea prevention. All of these medications kill adult fleas, while some will also kill the flea eggs and larvae that are in the environment.

Adult fleas make up only about 5% of the total flea population. Most fleas are in the environment as flea eggs, larvae, and pupae. Therefore, it can be helpful to treat the environment as well as your cat. There are many different environmental flea control products, but make sure you consult with your veterinarian to find a product that is both safe for humans and pets.

Many cats with FAD get secondary skin infections. These need to be diagnosed and treated by a veterinarian. Skin infections are often treated with oral antibiotics and topical treatments such as shampoos, sprays, or creams.

Preventing Flea Allergy Dermatitis in Cats

The mainstay in preventing FAD is to have your cat on year-round flea prevention. Consistency is very important, and missing a dose can bring you back to square one.

Cats need to be on flea prevention for at least 3-6 months in a row to break the life cycle of the flea. Most of the flea population are in the environment (both indoor and outdoor) as eggs, larvae, or pupae. It can take up to a few months for a flea egg to develop into an adult. Therefore, as most flea medications only last for one month, you need to give the flea medication for at least 3-6 months to kill all of the fleas. If we treat for less than that, or miss a dose, adults may develop and infect your pet after the flea treatment has stopped working.

It is also important to treat all pets in the house, even indoor-only animals, as some animals are not allergic and can have fleas without showing any symptoms. Pets that go outdoors can also pick fleas up and bring them into the house.

Consistent year-round flea control is also important because, in many parts of the country, flea populations can live outside year-round. In areas with a cold winter, fleas survive inside buildings and on wildlife or other pets. Giving flea medication all year also reduces the possibility that we forget to start the medication at the beginning of flea season.

It is important to note that you should always use a flea product recommended by your veterinarian, and one that is labeled for cats. Some flea products labeled for dogs can be toxic to cats.

Some cases of FAD can be difficult to treat. Being consistent and knowing how to tackle the problem can solve many of the causes of treatment failure.

Top causes of failure to treat FAD include:

• Failure to treat all animals in the household
• Failure to treat consistently and year-round
• Failure to treat the environment
• Use of less effective over the counter flea products in place of prescription medications

Read more:

Common Skin Parasites in Cats

Why is my cat itchy?

Common Skin Problems in Cats

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