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Treating Fleas on Cats—By Dr. Leslie Brooks

Cat Fleas
Written by Dr. Leslie Brooks, DVM
—Veterinarian 🇺🇸

Fleas certainly are pesky little bugs. Even though they are very little, they can wreak so much havoc for both your cat and you.

They can also be extremely frustrating to treat and get rid of. Oftentimes, a cat owner gets fleas under control only to find them jumping around in the house again a few weeks later.

The key to effective flea control is understanding the flea life cycle. In this article, we will discuss the life of fleas, the danger of fleas, and approaches to effective flea management.

How Do Cats Get Fleas?

The most common type of flea that affects our pets is the cat flea, Ctenocephalides felis. Cats get fleas by going around other animals that have fleas. This can be another cat, a dog, a rodent, or some other wildlife.

Occasionally, we can bring fleas into our home environment if we have been around other animals or in the vicinity of other animals that have fleas. Then, the fleas will find the cat in the home to feed on.

Fleas prefer furry animals to feed on. And fleas love cats. So if there are fleas in your home, they prefer to be on your cat, not you. This means that even if you do not get flea bites and you are not seeing fleas jump on you, there could still be fleas feeding on your cat.

Also, just because you do not see fleas on your cat, does not mean they are not there. Fleas are extremely tiny, move fast, and are great at hiding within cats’ fur.

The Flea Life Cycle

Fleas have four life stages. These are important to understand when we think about how to effectively get rid of fleas. The four different life stages are:

  • Egg
  • Larva
  • Pupa
  • Adult

When an adult flea is on your cat, they lay eggs… many, many eggs. These eggs fall off of your cat and into your home. The eggs hide in bedding, carpet, cracks of hardwood floors… all over the place.

The larval stage hatches from the eggs and then feed on the flea feces that also fall of your cat and end up throughout your home. These larvae create cocoons within the floors of your home. Within these cocoons, they transition to the pupa stage.

It is this stage, the pupa, that is resistant to all forms of treatments (including insecticides). And the pupa can even remain dormant for months within your home. When ready, the adult fleas arise from the pupae. And thus, the cycle begins again.

This entire life cycle can happen within the timeframe of just three weeks. And fleas can lay hundreds of eggs!

Treating Flea Infestations

When we are treating flea infestations, it is important to break the flea life cycle in order to effectively get rid of the fleas. This involves killing not only the adult fleas but also either the egg or larval stages. We will discuss this more when we talk about flea preventative options available.

Be wary of products or companies that claim to kill all life stages of the flea or that cleanses your home of fleas. Remember… the pupal stage is resistant to all forms of treatment. However, there is something you can do to get the pupa out of your home, which we will discuss below.

Flea Prevention

Give your cat flea prevention all year long. Yes, all year long…. especially if you have had a flea problem before or recently. It is also a good idea to change up which flea prevention product you use.

Fleas are able to build up resistance to insecticides. And though it is more common to see resistance against the older products, fleas can build up resistance to any product. By giving your cat a different flea preventative every so often, you are decreasing the risk of getting stuck with resistant fleas.

Depending on the product, you may need to give it to your cat for them to eat, or apply it topically onto their skin. You may also choose to use a flea collar. There is a multitude of products available. Some work to kill only adult fleas, while others kill adult fleas and either the egg or larval stages. We’ll discuss this more below.


While nothing currently available can kill the pupa stage of the flea life cycle, vacuuming can be a great way to get rid of it. If you are trying to get rid of a flea infestation, vacuum often- daily, if you can. Then, empty the vacuum bag outside of the home, such as in an outdoor garbage can.

Do this even if you have hardwood floors. While the pupa will typically hide in carpet, they can also hide within the cracks of hardwood floors. The suction from the vacuum can be an effective tool to get them out of your house. Doing this can also help to get rid of the egg and larval stages, breaking the flea life cycle.

In addition to vacuuming, wash your cat’s bedding frequently- at least once a week.

Preventing Flea Infestations

The best way to prevent your cat from getting infested with fleas is to keep your cat on regular flea prevention.

Even if your cat is indoor only. It is not uncommon for cat owners who only have indoor cats to still deal with flea problems. Fleas can be tracked into the home on us, our clothes, and our shoes.

If there are dogs in the home, it is especially critical to keep cats on flea prevention.

Fleas will often come into the home catching a ride on the dog. When they realize there’s a cat, they will jump on and reside on the cat. Then, the cat becomes the reservoir for the fleas and maintains them within the home.

Flea Preventative Products for Cats

There are so many flea preventative products available these days. They come in different forms. And while some are labeled to only prevent fleas, others prevent fleas and ticks, and still, others prevent fleas and heartworms.

The most effective products available are the ones that require you to get them through your veterinarian’s office. These are the newest ones with proven efficacy against today’s fleas.

That being said, there are still some very effective products available over the counter without requiring a prescription from the vet.

While we will not delve into every single available product in this article, we will discuss the different formulations of flea prevention available and which products are the best within these categories.

Topical Products

Topical (“spot-on”) flea preventatives are those that you apply to the skin on the back of your cat’s neck. They usually come in tiny little vials that you squeeze the liquid out of. It is important to apply it only on your cat’s neck.

This is because if your cat turns their head and licks it off, it could make them feel nauseous and will certainly taste horrible, making them foam at the mouth from the bad taste. Don’t worry, though, they’ll be just fine.

You usually need to apply these once a month, but each different product will have instructions on the package for how often you need to give it. For the product called Bravecto, you only have to apply it once every three months. Some of the most effective topical products currently available are:

  • Activyl (kills adult fleas)
  • Advantage II (kills adult fleas and larval stages)
  • Advantage multi (kills adult fleas and larval stages)
  • Revolution (kills adult fleas)


There are also flea preventative medications available that you can give to your cat to take by mouth. They usually come in a tablet formulation. You could hide it in some tasty, canned food, or even in a pill pocket or piece of cheese.

For those cats who are very particular about what is hiding in their food, you may have to use a mortar and pestle to mash it up and mix in with their food.

Some of the more effective flea preventative products that come as oral tablets currently are:

  • Comfortis (kills adult fleas)
  • Capstar (only lasts for 24 hours; usually used in cases of severe infestation or Flea Allergy Dermatitis)


Historically, flea collars have not been very effective at preventing fleas. However, there is a newer collar available that seems to be working fairly well. It is called the Seresto collar. It lasts for up to eight months and kills adult fleas.

Be careful when deciding to put a collar on a cat, though. Some cats do not like collars and could hurt themselves trying to take it off. Active, playful cats could get the collar stuck on something and end up harming themselves. So, just be mindful of your cat and their antics with things around their necks.

***Never give cats a flea preventative intended only for dogs**

Always remember to only give cats flea prevention that is labeled specifically for cats. Dog flea preventatives often contain permethrins in them. These chemicals are extremely toxic to cats.

Also, if you put flea prevention on your dog, prevent your cat from going around your dog for the next 24 hours, especially if your cat likes to groom your dog.

Signs of permethrin toxicity in cats include seizures, muscle tremors and spasms, incoordination, and possibly death.

Flea Allergy Dermatitis (FAD)

Flea Allergy Dermatitis occurs when a cat is allergic to fleas. Plenty of cats can get fleas and not be itchy, and never really even lose much fur. A cat has a true allergy to fleas when they just get one or two fleas on them and they are itching like crazy, losing fur, and getting little bumps all over their body.

It is a very painful condition and oftentimes difficult to get under control. Cats with flea allergy will have the following signs:

  • Extremely itchy- licking, chewing, scratching
  • Losing fur, especially near the base of their tail, along their spine and tail, around their neck, and along the backs of their legs
  • Red, inflamed skin
  • Little bumps all over their body
  • Sometimes they may be so itchy they aren’t eating or drinking as much as usual, and may be a bit lethargic

Cats with this condition need to be on flea prevention all year long to help decrease the chance of them getting exposed to fleas. If you suspect your cat may have a flea allergy, you should have them evaluated by your vet for diagnosis and treatment.

When first diagnosed, they will usually be put on a regimen of effective flea prevention, antibiotics to treat secondary skin infections, and medicine to calm down their itch and the inflammation within their skin.

Other Problems Caused by Fleas

Treating and preventing flea infestations is also important because fleas can cause other problems than just itchy skin.

Flea Anemia

Even though flea anemia is more common in kittens, if an adult cat gets infested with enough fleas, they can become extremely anemic. Some cats will have so much blood loss that they are at risk of death if they are not given a blood transfusion. And kittens with fleas are definitely at risk of dying from blood loss.


Fleas are also the culprit in transmitting tapeworms (Dipylidium caninum) to cats. The little tapeworm actually lives inside of fleas. When cats groom themselves or chew at fleas, they will inadvertently often swallow and ingest fleas. When this happens, they get infected with tapeworms.

If your cat has tapeworms, you will likely see what looks like little pieces of white rice within their stool. You may even notice some rice-like substances underneath their tail or in the places where they sleep.

Tapeworms are more of a nuisance than super harmful unless your cat gets too many of them. Seeing tapeworms in cats’ stools are often the first indicator that a cat has fleas.

Cat Scratch Fever

The bacteria that causes Cat Scratch Fever (Bartonellosis) is transmitted to cats via the flea. The bacteria is called Bartonella henselae. While many cats live with this bacteria and have no problems, some cats can get sick from it.

It is also what we call a zoonotic disease, which means it can be transmitted from cats to people. It is more common for a human to get it from the scratch of a kitten who has recently had fleas, but adult cats could potentially transmit it as well.


My cat is very itchy and losing fur, but I don’t see any fleas. Why should I put flea prevention on her?

Fleas are extremely tiny, fast-moving, and difficult to find on cats. It is always best to be proactive and treat for fleas to be on the safe side, especially if your cat is very itchy. They may have a flea allergy, which means even if they get bit by a single flea, their skin will break out and they will lose fur.

My cat is indoor only, so why does my vet say I should put flea prevention on them?

Indoor only cats can get fleas as well! In fact, we see many indoor-only cats who get fleas or even have a flea allergy. Fleas can sneak into the home on us, our clothes, our bags, and our shoes. Also, if there are other pets that go in and out of the home, they could track in fleas.

My cat just has a few fleas. Can I just wait for them to die off and not worry about it getting worse?

Nope! It will get worse, and fast. Fleas can lay up to 50 eggs per day and they will continue to multiply. Soon you will have a very large flea infestation in your home and your cat could be at risk of getting severely anemic from all of the fleas.



Fleas can be very difficult to get under control. And they are more than just a visible nuisance- they can be deadly and transmit other diseases, so it is important to prevent them from taking over your home. But if keep your cat on effective flea prevention regularly and vacuum often, it can be done!

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