Flea Infestation in Cats


Fleas are irritating parasitic insects that reside and feed on the skin of animal hosts, including cats. Fleas are found worldwide and year round. Cats may be exposed to fleas at any time, but large scale infestations are easily prevented with a combination of monitoring, medication, and environmental controls. In many cases cats do not show symptoms of flea infestation. Fleas are usually diagnosed by identifying an adult flea or “flea dirt” in the cat’s fur. Finding a flea is not an emergency, but requires action to prevent the infestation from becoming more severe. 

Some cats are allergic to flea saliva and develop an itchy rash when bitten by fleas. Severe infestations can cause anemia. Fleas can also transmit infectious diseases like tularemia, cat scratch fever and feline tapeworms to humans, making prompt treatment of fleas an important public health concern.  Treatment of flea infestation involves treating both the cat and its environment in an effort to kill fleas everywhere they live. There are many flea products available for cats, both over-the-counter and by prescription. Cats are highly sensitive to many anti-parasitic medications, and improper use can be fatal. Even when used as directed, many flea products are dangerous and potentially lethal for cats. Dog products must never be used on cats. The best way to ensure a flea control product is safe for use around cats is to consult a veterinarian. 

Flea infestation can be prevented by using year-round flea medications. It is recommended that all cats remain on a flea preventative year-round, even if they live exclusively indoors.

Risk Factors

Fleas are a concern for nearly all pet parents. They’re very common in most temperate outdoor environments, particularly in shady and moist areas like under bushes, under decks, or in dense vegetation. 

Finding a flea on a cat is not an emergency, however steps must be taken in order to prevent further infestation. Additionally, fleas brought into the home can establish themselves in carpets, crawl spaces, or between cracks in hardwood floors. An established flea population in a household can be extremely difficult to remove. It takes at least three months of treatment to successfully eliminate an existing flea population. 

Flea-infested cats consume large numbers of fleas as part of their grooming process which can transmit tapeworms to the cat. Severe flea infestations can also cause anemia, due to severe blood loss from flea feeding.

Fleas pose a serious health risk to humans and other animals because they can transmit serious diseases such as plague, cat scratch disease, and tularemia. Year-round use of a veterinarian-approved flea product is recommended for all cats throughout their lives in order to: 

• minimize the risks for flea-borne illnesses in humans, and

• prevent the hassle and expense of trying to eliminate an established flea population

Possible Causes

Cats can be exposed to fleas at any time, even if they live exclusively indoors. Adult fleas on other infected hosts lay eggs which fall off into the environment which eventually hatch and go through a larval stage before pupating. Flea pupae can survive in the environment for up to a year, withstanding freezing, drying, and insecticides, while waiting for an appropriate host. Once conditions are suitable, the flea emerges as an adult and jumps onto a host.

Cats are exposed to fleas when they pass through or spend time in an environment where other flea-bearing animals have been. Although it is uncommon for fleas to feed on a person, they can use humans to “hitchhike” into the home and gain access to indoor-only pets. Outdoor cats are at a much higher risk of exposure to fleas.

Indoor environments also provide the ideal temperature for flea development, allowing them to thrive. Therefore, it is important to keep cats on year-round vet-approved flea preventative medications specifically for cats, even if they never go outside.

Main Symptoms

Cats do not always show outward signs of flea infestation, but symptoms can include:

• Adult fleas on the skin • Itching (Pruritis) • Flea dirt on the skin or in the bedding

Detailed Characterization

A flea comb can help pet owners identify adult fleas and flea dirt. Flea dirt describes small specks of host blood that are excreted by the flea as it feeds. It appears as small, black or dark red specks on the skin or in the cat’s bedding and turns red if it gets wet.

Severe flea infestations, particularly of small cats or kittens, can cause anemia due to significant blood loss. Symptoms of anemia include:

Lethargy • Weakness • Rapid breathing (tachypnea)Pale gums

Some cats are allergic to flea saliva, a condition called flea allergy dermatitis. These cats typically develop a rash with symptoms like:  

• Hair loss • Reddening of the skin • Crusting of the skin • Severe itching (pruritus)

Fleas carry the infectious form of tapeworms, allowing a cat to become infected when it ingests fleas during grooming. Tapeworm infestation is often asymptomatic, but outward signs can include weight loss and a dull, unkempt coat. 

Fleas are a primary source of exposure to tapeworms for cats, so the presence of tapeworms may suggest a co-infestation with fleas.

Testing and Diagnosis

Fleas are readily diagnosed by examining the cat’s skin and using a flea comb. Identifying adult fleas or flea dirt is sufficient to make a diagnosis. The absence of fleas upon examination does not rule out the presence of fleas or flea-borne illness.

Steps to Recovery

Treatment of fleas is a multi-step process involving elimination of the parasites from pets and their environment. Every pet in the home must be treated, as fleas spread to all animals in the household.

It is important to only use flea treatment medications under the guidance of a veterinarian because cats are highly sensitive to many anti-parasitic medications and improper application can be fatal. Using a dog product on a cat can be lethal.

Many over-the-counter flea control products are unsafe, even when they are labeled for cats and the instructions are followed. There are also many natural products that claim to work against fleas, but have no scientific evidence to support this. The best way to choose a safe and effective flea product is to get veterinary advice. 

Successfully eliminating an existing flea population takes at least three months due to the flea’s complex life cycle and the high number of offspring each flea is able to produce. 

With regular use over a period of several months, all eggs in the environment hatch and are killed, eliminating the infestation. Some topical products shed into the environment along with the pet’s dander to target eggs and larvae where they are found.

With very severe infestations, cleaning of the environment to physically remove eggs, larvae, and pupae can speed along the process of eliminating the infestation. Strategies for accomplishing this include: 

• Vacuuming or steam cleaning carpets, vehicles, and upholstered furniture

• Washing all pet bedding and soft toys in hot water and drying at the highest heat setting. With severe infestations, buying new soft items may be necessary

• Washing all human bedding • Keeping cats indoors 

For outdoor cats, strategies to make the yard undesirable to fleas will also help prevent re-infestation. Installation of fencing to prevent wildlife movement, removing piles of leaf litter, mowing the grass frequently, or trimming trees to increase sunlight are all environmental controls to minimize flea populations. Blocking off areas that are cool, shady or moist to prevent feline access is also helpful. 

Be cautious about using pesticide sprays in or around the home. Many pesticides are lethal to cats, so use only products recommended by a veterinarian or professional pest control service.


Fleas are contagious to mammalian household pets like dogs, cats, rabbits, and ferrets, as well as wild animals. They are primarily transmitted when the eggs from adult fleas fall off the host into the environment. 

  Adult fleas may also hop onto people to feed, but humans are not their preferred host. Fleas cannot successfully carry out their life cycle and maintain a population with only human hosts. Flea bites pose a significant human health risk, as up to 80% of fleas carry serious diseases such as plague, tularemia or cat scratch fever. Inadvertent ingestion of fleas can also lead to tapeworm infections, particularly in children.

Flea infestation is prevented by routine monitoring of pets for evidence of fleas, environmental controls, and year-round adherence to vet recommended flea control medication for all household pets.

Is Flea Infestation Common in Cats?

Fleas are a very common external parasite of cats. The level of infestation is controlled by adherence to robust flea control practices.

Typical Treatment

Flea infestation is usually treated by using antiparasitics (flea control products) and environmental controls. Secondary illnesses related to flea infestation (such as tapeworm infestation) are treated as needed according to current medical guidelines.

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