How to Kill Fleas on Kittens, Senior & Sick Cats - Cat Info Detective

How to Kill Fleas on Kittens, Senior & Sick Cats

Skye Blake-updated, white background

Greetings itchy feline brethren! Skye Blake here, sharing what I’ve found about killing fleas on kittens, senior and sick cats.

You have to handle their needs differently than healthy adult cats.

paw prints coming in from a distance

Let’s take a closer look…

The information here is for general knowledge… always see your vet with questions about your cat’s individual needs.

Who Is Skye Blake?

Skye Blake-updated, white background

Skye Blake, Cat Info Detective, is a curious cat researcher (not a veterinarian) who sniffs out expert, reliable sources about cats, studies their information, then passes it on to you! 

Sometimes there’s not enough evidence for easy answers, so Skye gives you all sides, explains the situation as thoroughly and clearly as possible, and links you to experts on each page. 

All sources are given at the bottom of each page so you can do more snooping. 

Special Care

Special care must be taken with any cat whose immune system is compromised and can’t handle medications or treatments a healthy cat can.

This is because the liver, kidneys, and immune system that are compromised can’t process things very well, keeping would-be medications in the cat’s body too long, making them toxic.


kitten posing for the camera

Kittens under the age of 14 weeks need special help to get rid of fleas.

Their bodies can’t yet handle flea treatments used for adult healthy cats.

Just like adult cats, kittens resist fleas better when they’re healthy, so giving them the best kitten food you can afford is key to a strong immune system that helps keep critters at bay.

kitten with mom

Mother’s milk is best if they’re not yet weaned, but if that’s not possible, check with your vet for advice on what’s best to use.

If you haven’t already taken your kitten to a vet, get it there right away.

Have a complete physical done and discuss with your vet how best to deal with the fleas.

sleeping ginger kitten

People often rescue kittens that are infested with fleas… a sign they are probably sick.

Since fleas suck their blood, kittens often will have anemia and can easily die.

If you don’t know what to do next, put the kitten in a safe, warm area (such as your laundry or bathroom), until you can get her to a vet.

vet holding kitten

Give her a towel-lined box or crate to sleep in and food, water and a litter box.

If she’s acting normal, eating, drinking and going to the bathroom, she should be fine until the vet visit. Just be sure to get there as quickly as you can.

If the kitten is lethargic (not moving much or having much energy), get it to a vet immediately.

It needs emergency care or it might die. If it’s after normal hours, an emergency vet should be available in most areas.

How to Kill Fleas with a Kitten Flea Bath

tabby cat being bathed, groomed

Bathing kittens and using a flea comb afterward is the best method for ridding them of these pesky pests.

Hannah Shaw, The Kitten Lady, has an excellent video that explains how to bathe kittens…

Ask your vet if he can bathe and treat your kitten if you’re not sure how to do it.

kitten asleep on lap

Often vet techs and groomers will be happy to show you.

Just as with healthy adult cats, combing your kitten with a flea comb and keeping your house clean helps a lot with controlling fleas.

See how to do this at “Ways to Get Rid of Fleas on Healthy Cats!“.

Senior & Sick Cats

senior tabby cat

Cats show signs of age at individual rates but there are a few categories used to describe older cats.

When dealing with fleas, your approach is the same for each age group.

Mature (7-10 years)

Senior (11-14 years)

Geriatric (15+ years)

Be extra careful dealing with fleas on your older cat. Prevention is your best weapon with fleas.

ginger tabby sunning on a fence

Most likely, you and your feline buddy have been together a long time.

He’s worth the extra care, isn’t he?

There are a few steps to follow to be sure you keep him safe while making him flea-free.

The first step is the most important… take your buddy to the vet for a checkup.

person petting a tabby cat's head

Even if he seems healthy, he could have chronic diseases such as diabetes or “silent” conditions that affect the kidneys, liver and immune system.

That means his body can’t process and eliminate toxins very well anymore.

This could cause serious reactions, such as difficulty breathing, rashes, or seizures, if you apply flea sprays, shampoos, or other treatments, whether “chemical” or “natural”.

Don’t Put Any Flea Killer on Your Cat Without a Vet’s OK!

"no" sign

Discuss any flea treatment with your vet to be sure it’s safe and effective for your cat.

Every cat’s medical situation is individual, so it’s best to discuss it with your vet before using it.

Your vet will help you figure out the best way to kill the fleas depending on your buddy’s current health and the health of your wallet!

Vets also know the latest treatments available, whether prescription or over the counter, and which are best for vulnerable older or sick cats.

Treat all flea products as medication and apply carefully according to the instructions.

Don’t Ever Use Dog Flea Treatments on Your Kitty

cat reaching up to dog's neck

Dog flea treatments are only for dogs!

Formulations and dosages are unique to a dog’s body and can kill a cat, especially one with a weak immune system, kidney or liver diseases.

If you have dogs in the house, talk to your vet about treating them with things your cat can’t lick off.

Practical Ideas for Getting Rid of Fleas

black & white kitten

There are a few practical things you can do to kill fleas and keep them off your kitten, sick or elderly kitty.

It’s all the same as you’ll do for healthy cats…

The Flea Comb


The best tool in your arsenal is the flea comb and a bowl of soapy water. 

Those little buggers jump so fast you’ll never catch ’em.

Dump those fleas in the bowl of water as you find them. Just be sure you’re gentle and careful.

flea comb

Here’s a short YouTube video showing you how to use a flea comb…

Don’t get anything in her eyes, ears, mouth, or nose.

If your kitty is heavily infested with fleas, you’ll need to use more than a flea comb.


Your buddy won’t sit still long enough to get them all combed out… not fun for either of you!

Bathe your cat carefully, if you decide you both can handle it, so your buddy won’t get sick (or sicker) from it.

Check with your vet on the best treatment for any older or sick cat.

You can find flea combs at pet stores, some grocery stores and online (Amazon, Walmart, Chewy, etc.)

Wash, Vacuum, Repeat!

wash bedding, etc. to kill fleas

Check all areas where your cat loves to hang out.

Wash all bedding (theirs and yours), throw pillows, furniture covers, window seat cushions, curtains, cat toys (especially plush ones), and anything else that can go in a hot water wash. 

Clean all litter boxes and change the litter daily until there are no more signs of fleas.

2 cats looking in litter box

Wash your hands after petting any animals in your household.

To clean cat trees, sofas, chairs and other furniture, vacuum the entire thing, including underneath, and use furniture shampoo for attached cushions.

Throw out things you can’t clean. 

Whatever you’re throwing away, seal in plastic bags to keep the fleas contained and get it in an outside trash bin immediately.


cleaning supplies for killing fleas

It’s very important to thoroughly vacuum all floors and furniture in your house and cars, including baseboards and crevices.

Vacuum and shampoo any cat trees thoroughly. Make sure it’s dry before letting your kitty back on it.

You’re getting rid of flea eggs, larvae, pupae, and adults by doing all this.

vacuum cleaner

It’s the best way to kill the fleas and keep the cycle from repeating itself.

If your vacuum is bagless, spray some vinegar in the tank.

Be sure to use the attachments that let you get into corners, cracks and crevices to get flea eggs.

Clean the tank after every use.

drawing of a vacuum cleaner

I highly recommend getting rid of wall-to-wall carpeting, especially shag.

If you have to have a carpet, use area and throw rugs over hardwood floors… stylish and much easier to keep clean.

Move furniture around to get underneath it.  Turn it over to clean the bottom of the sofa or chairs. 

If your kitty likes to hide in the sofa or chair lining, take it off and throw it away before cleaning the underside.

ginger, white cat standing by cleaning bucket

If you want to spray flea killer around the edges of the rooms, in the car, and on the cat’s favorite spots, check with your vet first.

This includes using diatomaceous earth (DE) or salt.

Very young, sick, and senior cats often can’t handle any sprays in their world, whether “chemical” or “natural”.

Cleaning Your Car

white car interior; clean to kill any fleas

If the cat was in your car, carefully vacuum the inside and wash the seats. 

You can use the same products on the car rugs as you use in the house. 

Be sure to ask your vet if they’re ok to use in this situation.

If you don’t clean the car, you’ll probably end up bringing more fleas in the house and you’ll have to start all over again!!

Get Help If You Need It!

cleaning lady

Enlist all the help you can get from family members and friends if it becomes overwhelming for you. 

DON’T SKIP the vacuuming and cleaning steps or you’ll never get rid of the fleas!

If you can’t do it all yourself and can afford it, you could hire a professional cleaning service.

unhappy cleaner

Repeat regularly… daily if you have a flea infestation.

These steps will help keep all stages of fleas (along with diseases and tapeworms) from transferring to you, your family, and other animals.

Advice From Experts: Killing Fleas on Senior Cats

veterinarian listening to a cat's heart; health check for sick, senior cats; get rid of fleas

I found some helpful comments at from vet experts:

Letrisa M. Miller, Feline Veterinarian, About Killing Fleas on Geriatric (Older) Cats:

“There are at least two products that are not harmful to geriatric cats if used according to directions. Having fleas is definitely harmful to geriatric cats!

Cats that have fleas almost always have tapeworms and can get some nasty diseases that are carried by fleas such as red blood cell parasites/infections and Bartonella infections (cat scratch disease).

tuxedo cat with mustache

There are at least two products that are not absorbed into the body: imidacloprid (stays in the oil on the surface of the skin) and fipronil (does enter oil glands, but goes not further).

These are safe for geriatrics as long as they don’t ingest them [emphasis added]. 

Some cats do not like the carriers that these products are in or the scents that have been added to the products and can be upset by this for some time after application.

black cat sunning himself; flea treatment

It is also very important that the products are applied on the back of the neck on cats, not over the shoulders as on dogs. 

If applied over the shoulders, cats can turn around and lick the area the product was applied on and ingest the product.

The other ways that spot-on products can be ingested after application is a housemate grooming the product off of another cat or dog or the cat’s scratching the spot [where] the product was applied and then grooming the product off of the foot [emphasis added].

Organophosphates, Pyrethrins & Cats

flea spray bottle; treatment

Organophosphates and pyrethrins are not very safe for any cat, although pyrethrins are safer than organophosphates.

These are older products that have been on the market for decades and have been causing deaths for decades.

They also do not do a very good job of killing fleas!

calico cat licking paw; killing fleas

Avoid these scrupulously in geriatric cats, as they require metabolism and/or clearance by the liver or kidneys to remove the product from the body.

I would not recommend using any over the counter flea products without consulting your veterinarian first.”1

Julia Jamine, Retired Licensed Veterinary Nurse:

various chemical flea treatments

“For older cats that do not groom themselves as much [as younger cats], fleas can cause anemia or low red cell counts.

This can lead to a necessary blood transfusion and a strict flea treatment regimen that the cat, being weak, may not take… well… [It would be better to keep] the fleas [from] getting out of control.

I have seen cats with heavy infestations and when you bathe them to kill the fleas the water run[s] red from all the bloody flea feces. 

drawing of a flea; getting rid of fleas

The vet above [Letrisa Miller] has the perfect solution; to use Advantage or Frontline exactly the way she describes it.

Oh, and “natural” alternative[s] can be worse than vet recommended treatments [emphasis added].

Many natural treatments have either pyrethrins or citrus oils that can be poisonous to cats.

cat sleeping on a cat tree; flea treatments

The only way to kill the fleas that may be on the cat is with poisons; many… fleas have evolved resistance to the natural poisons… [These] chemicals will not kill off the fleas, but… can still hurt the cat if the cats ingests [them].

In order for [a] natural treatment to work your cat must be covered in it head to tail, whereas the other treatment [spot-on] is applied only on the back of the neck.2

black tabby watching something

John Duncan, D.V.M., Small Animal Medicine and Surgery, The University of Georgia College of Veterinary Medicine:

“Different diseases of old age, such as chronic kidney disease or hyperthyroidism, may have different implications for the use of flea treatments.

Kidney disease is difficult for all treatments because the kidney is required to excrete many substances to avoid toxic buildup.

vet holding tabby cat; killing fleas

Since dosages are calculated for healthy kidneys, normal dosing could cause high blood levels of a drug in animals with kidney disease.

Therefore, for animals with kidney disease, flea treatments should be started under the direction of a veterinarian and the animal should be actively monitored for toxicity.”3

Special Needs Means Extra Care in Dealing with Fleas

ginger cat scratching; getting rid of fleas

The info I’ve uncovered tells you one main thing to know when trying to kill fleas on cats with special needs.

You have to be extra careful when trying to kill fleas on kittens, sick or elderly cats. Their bodies aren’t able to tolerate the same products as healthy adult cats.

This is true for both “chemical” and “natural” treatments.

mama and kitten

Take your kitty to the vet for a checkup and get their help to figure out what’s best to do. That way you’ll know you’re doing the right thing for him.

Being cautious is the best way for your buddy to have a good long life.

You should be able to keep fleas to a minimum if you comb your fabulous feline frequently with a flea comb.

Vacuum and clean your house regularly since this will kill the adult fleas before they can lay eggs in your house.

vacuum cleaner head; getting rid of, killing fleas

This will keep the nasty cycle from repeating itself and you’ll have a happy life with your best feline friend.

If you’ve discussed options with your vet for treatments on your kitty, you should check the pages below for more info about “chemical” and “natural” treatments.

Remember, “natural” is not necessarily safer.

Discover more about dealing with fleas, ticks, and treatments at “Cat Health“.


Sources used on this website are either primary or secondary.

Primary sources are always preferable and have the most reliable information because they’re original and directly referenced.

Scientific abstracts and data are good examples of primary sources.

Secondary sources are weaker because they usually consist of opinions or articles that give no sources of their own, although sometimes they refer to primary sources.

When I use secondary sources, most are those with some authority, such as veterinarian or cat behaviorist books and articles.

List of Sources

“Are Flea Treatments Harmful for Geriatric Cats?”,

“Die Fleas!…Freaky Cheap Flea Control”, by Paul Wheaton, Richsoil

“Flea Control and Prevention for Senior Cats”, by Robin Rockey, Chewy

“Fostering 101”, Hannah Shaw, Kitten Lady

“How to Get Rid of Fleas on a Kitten Too Young for Topical Ointments”, Co-authored by Pippa Elliott, Wikihow, MRCVS, Updated: March 29, 2019

Updated April 14, 2024

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