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How Do Indoor Cats Get Fleas?

Why is your cat scratching themselves like crazy? They are strictly an indoor cat and there’s no way your cat has fleas…right? Even if your cat lives indoors, they are still at risk for sneaky fleas. Dr. Jess describes how indoor cats get fleas and how you can treat an infestation in your own home.

cat scratching itself

What is an Indoor Cat?

In relation to this article, we will define an indoor cat as: Indoor cats are cats that are strictly indoors, no time spent outdoors or out of the house.

This means that, for example, if your cat goes outside on your front porch while you have your morning coffee, they are not an indoor-only cat.

They would be considered an indoor-outdoor cat.

Everyone has their own description of what an ‘indoor cat’ is, but for the purposes of this article, this is what I will consider as an ‘indoor cat’.

Many see having indoor cats as a safer option for many cat owners and their feline friends.

Keeping your cat indoors can help prevent them from getting lost, getting hit by cars, from getting into fights with other animals, and from a whole host of other harmful health and medical issues.

Why Do Cats Itch and Scratch?

Cats can scratch for a multitude of reasons, just like humans can scratch or feel itchy for different reasons.

Cats can have dry itchy skin, where you may see scratch, rubbing, and flaky skin.

Feline friends can have allergies, such as food allergies or chemical allergies to household cleaners, that can make them itchy and scratch.

Itchy, inflamed skin is called dermatitis.

Other times, kitties can become itchy from external parasites, such as fleas.

What Are Fleas?

Fleas are a small external parasite that are flightless, but can jump and leap incredible lengths compared to their body size, and have narrow bodies which help them navigate through fur and hair.

They also have chewing mouthparts to consume debris from the surface of skin and for piercing to consume blood, which is needed for the flea to thrive.

They need a warm host (or body) to live off of and survive and reproduce.

Fleas range from the size of a pinhead to an eighth of an inch long, and are typical very dark or brown-looking in color.

The most common flea that is found on cats is Ctenocephalides felis.

Cat fleas love and thrive in warm, humid climates, like on living bodies.

Flea Life Cycle:

Fleas are considered an external parasite (or ectoparasite), meaning they complete their life cycle on the outside of a host. Once the flea is no longer able to live on the host, the flea will die.

Cat fleas have 4 life stages that they go through. According to the CDC’s website regarding flea life cycles [source]:

  1. Eggs: “Eggs are shed by the female in the environment.
  2. Larva: Eggs hatch into larvae in about 3-4 days and feed on organic debris in the environment. The number of larval instars varies among the species.
  3. Pupae: Larvae eventually form pupae, which are in cocoons that are often covered with debris from the environment (sand, pebbles, etc). The larval and pupal stages take about 3-4 weeks to complete.
  4. Adults: Afterwards, adults hatch from pupae and seek out a warm-blooded host for blood meals.”

Then another full cycle can begin again and again.

Can Fleas Be Dangerous to Cats?

Infection: Cats frequently scratch themselves, and can be seen in most cats on a daily basis – no big deal!

However, the kind of scratching prompted by fleas is in a class all of its own.

Ceaseless scratching can lead to open scratches or wounds, that in time, can lead to infected wounds, which can turn into whole-body, deadly complications.

Dermatitis: Flea allergy dermatitis is caused from an allergic reaction from the saliva of the mouthpart of the flea. The animal is allergic to substance in the saliva and a skin reaction takes place. The dermatitis, or inflammation of the skin, from this allergic reaction, can caused red, raised bumps or rashes, red patches of skin, itchy and scratchy skin areas.

Anemia: Another potentially dangerous issue with fleas has to do with their blood-sucking quality. Fleas suck blood through the skin of their host. This poses special risk to cats, and more notably kittens, who can be more likely to develop anemia as a result of the blood loss in extreme flea infestation cases.

Disease Carriers: Fleas are also disease vectors (disease carriers/transmitters) for bacteria. Cats can become disease traffickers after being bitten by carrier fleas.

Cat fleas can carry diseases that affect other cats and humans….

Common Feline Diseases Carried by Fleas: 

  • Tapeworms: Fleas also carry a parasite called the tapeworm, Dipylidium, which is easily treatable. They are commonly found in cats that have been exposed to fleas. [source]
  • Haemobartonellosis (Mycoplasma Haemofelis): Fleas can also be vectors for a bloodborne parasite called Mycoplasma Haemofelis in cat’s. This bacteria is known to cause anemia, fever and other medical concerns. [source]
  • Bartonella species infections: Also known as “Cat-Scratch Disease” is caused by a bacteria named Bartonella henselae, which a cat can contract via fleas. If a cat with Bartonella ‘scratches’ a person and leaves an open wound, there is a potential for the exposed human to contract the disease as well and show symptoms of fever, headache, and wound infection. [source]

How Can Fleas Be Detected and Diagnosed?

If you observe your cat scratching and aren’t sure if fleas are the cause, you should contact your vet to set up a time to bring your scratching cat in for a veterinary exam.

The veterinarian will likely use a flea comb on your cat and observe if tiny black dots are present.

These black specks are commonly called “flea dirt”, but in reality, it is the excrement that the flea leaves behind on the skin of the host.

Many times, a thoughtful observer will see this flea dirt and think that these are the actual fleas themselves, when in fact, they are not.

If you find the black specks, smush some in between a damp paper towel. If it is flea dirt, the ‘dirt’ will turn the wet paper towel a rusty red color.

The reddish coloring on the moist paper towel is from the residue from your cat’s blood that was previously consumed by the flea and partially digested and then excreted onto the skin of your cat.

However, sometimes, moving, living, jumping fleas can also be observed.

Common areas where fleas and flea dirt are observed are at the base of the tail (lower back area), neck, and back legs of the cat.

Fleas are very good at hiding on a cat’s body.

If someone doesn’t see them, it doesn’t mean that they aren’t there, because fleas can be present in small numbers, and many times, the flea or flea dirt is simply not observed at that particular moment in time.

Treatment For Cat With Fleas:

If you’ve been under the impression that your feline friend does not need flea and tick prevention because you think their indoor lifestyle will protect them from these parasites, you could run into troubles.

I will discuss the ways in which indoor cats can get fleas in the section below.

Contact Your Vet:

If you think your cat currently could have fleas, there are a couple of different options and approaches to treating the flea infestation that you should talk to your veterinarian about immediately.

How do you ensure that the fleas cannot complete their life cycle? Well, this is where your veterinary medical team gets to work!

Veterinary clinics are full of very knowledgeable staff that know a lot about what products are safe and effective for your pet.

If there are fleas on your cat, fast and quick action is best. Contact your veterinarian for treatment options ASAP.

Use a Flea Comb:

Your first job will be to eliminate as many fleas by combing and bathing your cat. 

Use a flea comb to remove as many fleas as possible, and vacuum frequently to remove the fleas and their eggs from your carpets and floors. Make sure to take the vacuum canister or dust bag outside immediately.

Give Cat Flea Bath:

Many cats do not tolerate baths very well, so do not force this step.

Many veterinary offices can also help with this step – with the proper staff and techniques to get the job done safely and quickly for your cat.

However, flea combing, flea baths and shampooing together, are not enough to get rid of a flea problem.

There’s more that needs to be done on your part!

orange tabby cat in bed with owners

Clean Your Environment:

The only way to rid a flea infestation is to remove the fleas from your cat AND your home.

Despite the numbers and choices of commercial flea-killing products out there on the market, removing fleas from you and your cat’s lives is harder than it sounds.

Not only do you need to remove the fleas from your cat, but you need to remove the fleas from your home so that they can’t re-infest your cat.

Then after removing the infestation in your home, you must prevent fleas from taking stake on your cat ever again, by using flea preventatives, which I’ll talk about here in a sec….

Cleaning and vacuuming your home thoroughly is one part of the equation when it comes to ridding your home of this gross parasite.

I always recommend getting the help of others for this major task, hiring professional cleaners to help you.

Also- consider hiring a professional exterminator.

Treating Your Home For Fleas and Flea Eggs:

Cleaning needs to be an ongoing task while the adult flea treatment is killing the live fleas in your environment.

  • Vacuum carpeting daily and dispose of used vacuum bags.
  • While your focus is on the floor, clean the baseboards, where fleas love to hide, thoroughly on a daily basis.
  • Wash all bedding thoroughly.  While the bedding is free of coverings, vacuum the mattress, particularly in the crevices, where eggs might hide.
  • Steam-clean carpeting will kill any remaining eggs the vacuum might have missed.
  • Launder all drapery, pillows, cushions, and all clothing in the home.
  • You may choose to do a flea or insect treatment in the home. I recommend hiring a professional and asking them to use pet-friendly products.
veterinarian doctor writing a prescription

Flea Medications:

Once the bulk of the fleas are gone, you can prevent further flea infestations with the use of veterinarian-recommended topical or oral flea control products, remembering to NEVER use dog flea products on your cat as some are toxic to them and can cause severe illness to your cat.

Read all medications labels very carefully before administering to your cat and always ask your veterinary staff any questions prior to giving flea treatments.

Flea treatments work by interrupting the flea’s life cycle in some way.

An important thing to remember is that there are different stages of the flea life cycle: egg, larva, pupae, and adult.

Therefore, to ensure that the flea infestation does not continue in your home, you must treat all pets in your home for three full months.

This three-month treatment will help to ensure that the flea’s life cycle is disrupted, no matter which stage that the of the flea life cycle the flea is currently in when the cleaning and treatment of your home occurs.

You do not want sneaky little larvae or pupae hatching and turning into adult fleas further on down the road!

Topical Feline Flea Treatment Options:

Below are some examples of some topical flea products available for your cat.

  • Advantage: This uses imidacloprid as the active ingredient, and is generally regarded as safe for cats and kittens over 6 weeks of age. It does not kill ticks.
  • Frontline: Claims to kill both fleas and ticks, Frontline uses fipronil, a synthetic ingredient, which may cause temporary sensitivity in the area of application. 
  • Revolution: Its main ingredient is selamectin, which is said to kill not only fleas and some ticks, but also ear mites, as well as offering protection against preventing heartworm infestations. Revolution stays in the bloodstream, and should not be used on kittens under 6 weeks of age.
  • There are many other brands out there, however, these are the three most common brands that my past clients have used on their pets.

Always make sure that whichever product that you pick, that it is one recommended by your veterinarian.

Also, make sure that the product that you have is the correct weight category for your cat, as most topical flea products are based on the pet’s size/weight.

Also, be extremely sure that the flea product you are about to put on your cat is NOT the dog version of one these products as these can be toxic to felines.

Follow all of the package directions for your age/size of the cat, and ask any questions you may have about the product or its administration to your vet BEFORE applying the product to your furry friend.

So Why Do House Cats Get Fleas?

There is no way that was a flea…

Indoor cats don’t get fleas, right?

WRONG friend.

I have had to tell this to so many clients I have had throughout the years….

Yes, your indoor-only cat does have fleas, and here’s how.

Even with our best efforts, fleas can enter our homes, and therefore, our cats too. Turns out that it’s pretty darn easy for these little pests to get inside our houses!

A home is not a sealed environment – people and pets come and go, doors and windows open and close.

As I discuss some common ways fleas get inside and onto your pet cat, keep in mind that a single flea can jump more than 160 times its own body length. [source] They are also quite small and nimble creatures.

These facts will make the points below seem even more feasible for these little buggers to jump right into your lives.

Other Pets:

Do you have any other pets in the house?

Because they just may be your “patient zero” in the case of your flea problem.

Your other pets may be the culprit here.

Even if your other pet is another indoor cat, the chances of your pets becoming infested with fleas goes up dramatically for every additional living animal or being in your house. (That includes you! I’ll come back to that in a minute.)

So – why does this happen? Why do the chances of getting fleas rise because there are more animals in the house?

Think about this for a second – every living being gives your household more of a chance to bring in fleas, be a good host for the fleas, and transfer the fleas to even more living, breathing bodies in your home.

Maybe you have a dog too and your dog goes outside for while, picking up a flea before coming back into the house.

The outdoors can easily become infested with fleas espcially during warm weather months, and in areas with known populations of dogs, cats, small rodents and mammals, and birds.

Because every time a pet goes outdoors – or even close to the door itself, they’re at an increased risk of picking up a “hitchhiker” or “flea-loader” flea from the outdoors and bringing it inside where it can find a nice spacious host, your cat!

Even if your other pets are already on flea preventative, a hitchhiker flea can tag along for a ride inside your home for a period of time.

Many flea and tick products take some time to kill the bug, and even those that repel the fleas, may not repel a flea for a quick trip through the threshold of your front door.

Even if only a few fleas are brought inside, the insect can lay thousands of eggs.

Just one pregnant flea can quickly lay 50 or more eggs and then the cycle expands, gets worse, and continues and continues on and on until a full treatment plan is strictly enforced and followed, stopping the infestation in your home.

pet at the vet clinic with owner in waiting room

Vet Visits and Pet Groomers:

There will be times in your cat’s life when they have to leave the house.

The vet’s office, boarding facilities, and/or the pet groomers are just a few common examples.

No matter how clean your vet’s office, boarding facility, or grooming salon is, fleas are exceptionally good at hiding.

Taking your indoor cat to the vet for a simple well-check or vaccination can expose them to fleas, flea eggs, and flea larvae, all of which might be carried home unbeknownst to you and your kitty cat. 

Windows, Screens, and Doorways:

Fleas are so small and nimble that they can come into your home on their very own.

They can use their legs to leap through screens or coming in through the smallest cracks of windows and doors.

So your kitty that likes to take their cat nap by that sunny window sill, or that observant cat that watches and stalks the squirrels running around outside your front door – are all at risk of that one pesky flea marching right on in and causing an itchy uproar in your home.


Anything, or anyone, can bring a flea into your home.

I’ve already discussed how fleas can hitch a ride on your pet’s that live in your home.

The same is true with you, your family members, and any guests that may enter your house. This could mean visiting friends or family members, your house cleaners, a pet sitter, or delivery drivers, such as grocery-delivery service providers.

Fleas are happy to leap on your socks, jump onto your pants, and overall go for a joyride on your clothes, just like ticks do.


If there are rodents in or around the home, they have the potential to drop flea eggs where your cat likes to hang out. Those eggs can then find your feline friend and have a party on your cat.

New Home / Environment / Furniture:

Pre-existing fleas from pets living in the home before you, can be dormant for months, so if you’re moving, they could just be waiting for your cat to arrive.

Another thought to keep in mind is if you buy second-hand furniture, bedding, or rugs from someone whose pet currently has or has had fleas, you might accidentally bring the pests into your home.

cat laying on sidewalk scratching itself with back leg

Can Fleas on Indoor Cats Be Prevented?

In order to prevent a flea infestation on your indoor cat, make sure to keep up with their regular flea preventive medications year-round.

Your veterinarian can help you decide which flea preventive medications — topical, oral or collar forms— is best for your cat AND your family’s lifestyle.

Additionally, check your cat’s coat routinely for fleas or for “flea dirt”.

If you notice your cat scratching a lot, especially around the neck, back, and base of tail areas, then it is likely time to contact your vet for a closer inspection on what is going on.

Regularly cleaning your house from top to bottom is another activity that can help prevent the infestation of fleas in your home.

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