Written By : M Samy

What to do after giving cat flea treatment ?

After giving flea treatment to your cat, you should monitor him/her for at least 2 to 4 hours after the product has been applied to prevent your cat from licking it off before it dries to avoid any risk of poisoning or overdose.

How long to leave flea treatment on a cat?

What to do after giving cat flea treatment ?

Although some cat flea treatments, that you can apply yourself, will get rid of fleas within a few hours of application (sometimes less than an hour), to ensure that all fleas are dead, it is always advisable to leave the flea treatment on your adult cat for 24 hours and a little longer if it is a specially dosed treatment for kittens under 8 weeks old (the product is weaker and it takes longer to eliminate the fleas)

Do I need to isolate my cat after flea treatment?

Yes, it is best to keep your cat confined to the same room for at least 24 hours after treatment for the following reasons:

  • Other pets may accidentally lick the flea product, which could poison them (even if you have a baby in the house!)
  • To prevent your cat from going outside and being exposed to the elements (water, air and light) which will diminish the effect of the active ingredients in the flea medicine.
  • To prevent fleas from falling off the treated cat and jumping onto another pet or hiding in your furniture.

Do fleas fall off cats after flea treatment?

Fleas do not fall off cats after flea treatment, some of them maybe, but, the flea eggs and larvae may fall off hours after applying the product (the result of excessive itching /depending on the product used) so it is a good idea to confine your cat to the same room for at least 24 hours as some flea treatments do not kill the eggs which may fall off and hatch in your home and return to your cat’s back after a few days.

How to get rid of fleas on cats after treatment?

Even in winter, fleas have many ways to get to your cat, you should use a flea comb to remove dead or dying fleas from your cat’s fur, and after brushing your cat, bathe him with a flea shampoo like Adams Flea & Tick Cleansing Shampoo to remove the eggs laid during the last 24 hours.

Do not use dish soap excessively when bathing your cat, it is meant for degreasing and will remove the oils that protect your cat’s skin and coat.

How do I know if my flea treatment is working?

After about half an hour of applying the topical flea medicine to your cat, the fleas will start to move around and you will see them moving around on your cat’s fur, a sign that they are dying.

How long does the flea pill take to kill fleas?

After applying an oral flea treatment, fleas will start to die within 30 minutes and after one day to 48 hours if you treated your cat with a topical flea medicine. This also will depend on the flea medicine brand, the dosage and conditions of use. 

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Topical flea treatments kill fleas after contact with the active ingredient and this may take some time for the flea medicine to spread over the cat’s skin.

For example, usually Frontline Plus begins killing fleas 4 hours after application and Advantage after 10 to 12 hours.

On the other hand, oral flea treatments will start killing fleas only 30 minutes to 4 hours after application, but this type of product will only kill the fleas that bite your cat.

You will get slower results when you use natural cat flea treatments.

How do flea treatments work ?

1.How do Topical cat flea meds work?

Pyrethrins, Pyrethroids, Fipronil, Metaflumizone, Selamectin as well as Imidacloprid used as active ingredients in topical cat flea treatments will first disrupt the nervous system and the proper functioning of the flea’s nerve cells and make their movements impulsive and eventually kill them.

Other spot-on cat flea treatments contain active ingredients such as Rotenone which will paralyze the fleas and suffocate them by preventing oxygen from reaching their cells.

Finally, there are other flea meds that use D-limonene, and linalool as active ingredients that work by softening the fleas’ shells which will dry them out and eventually kill them.

2.How do Oral flea meds work?

The active ingredients in oral flea meds are usually either :


This molecule will end up in the fat cells of the cat’s skin and in the stomach and blood of adult fleas afterwards.

Lufenuron will not kill the adult fleas but will prevent their larvae from producing a hard shell which will eventually kill them.


There is another active ingredient in oral cat flea medicine, Nitenpyram, which blocks the nerve receptors of the fleas and kills them in less than an hour (usually in 30 minutes).

How long will I see fleas after flea treatment?

Not more than 24 hours if the flea medicine used eliminates the adult fleas, larvae and their eggs. Some products do not break the flea life cycle and not kill the eggs and these may fall off your cat, hatch in your carpet and rise on your cat’s back after just a few days.

Try to follow the instructions when using the flea treatment and brush and wash your cat thoroughly after 24 hours and don’t forget to use the flea spray and vacuum to remove the fleas, their larvae and especially their eggs from your cat’s bedding and furniture.

Can I comb my cat after flea treatment ?

Yes, you should comb your cat but only after the flea treatment has finished removing all the fleas, i.e. the next day (after 24 hours) so that you don’t risk dropping any fleas or eggs that are still alive and can escape and hatch in your carpet.

You will use a fine-toothed metal flea comb to brush your cat from head to tail and you will before this operation which must be repeated for at least one week, spread a sheet on the floor, put your cat on it before brushing him to recover and get rid of all that will fall from his fur.

Can I pet my cat after flea treatment ?

Your children should never be left alone with the cat until they have been brushed and bathed a day after the application of the flea treatment, especially spot-on ones.

You risk almost nothing if the flea treatment gets on your fingers (you just have to wash your hands) but you have to refrain from peting your cat especially in the spot where you applied a topical medication at least until it becomes dry) and it would be best to wait a day or two for other reasons like:

  • To avoid removing some of the flea medicine which would diminish its effect
  • To avoid the risk of dropping live fleas, their larvae or their eggs on your bed or your carpet
  • To avoid the risk of having your fingers impregnated by the product and to deposit this product on other parts of the body of your cat where it will be able to lick it and to risk poisoning.

If you have used an oral cat flea treatment, you can cuddle your cat but the risk of dispersing the flea eggs is still high as they may fall out on their own without brushing.

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It is also for these reasons that you should avoid sleeping with your cat after flea treatment.

How long after flea treatment can I bathe my cat ?

24 hours is the time it takes for the flea treatment to get rid of all the fleas, their larvae and eggs. You should never bathe your cat during these first 24 hours because the active ingredients in spot-on flea medicine are Pyrethroids (synthetic version more toxic) or Pyrethrins (natural and safer for cats), and these molecules become ineffective once exposed to water, air and even light although they are combined with other chemistries to protect them from the outside elements and prolong their activity time

How long should I keep my cat in after flea treatment ?

It is recommended that you keep your cat out of the house for at least 24-48 hours after flea treatment, especially if you have used a spot-on option, as this medicine can lose its effect if exposed to water or moisture, light or even air.

It is also recommended that your cat remains at home for at least 4 to 7 days to ensure that the dose used has done its job and your cat is free of fleas and eggs. 

So, the next time you treat your cat, you will increase the dose a bit if the fleas don’t die within the first 48 hours and you’ll never know if your cat goes out and brings back new fleas from your backyard.

On the other hand, after the treatment has started working, some fleas or their eggs may leave their host before they die and it would be wise to confine your cat to one room for the first 24 hours in order to vacuum and eliminate any chance that these eggs will ever hatch and infest your cat again.

So the answer to the question “Should I let my cat out after flea treatment? Keep your cat under visual observation for 24-48 hours after the treatment and do not let him out for the first week, especially if this is the first time you have given him flea treatment.

Can I reapply flea treatment early cat?

No, it is not safe to reapply flea treatment early, which means before 30 days and if even after this treatment you still find fleas on your cat, it is because you did not use the right product:

  • You did not use the right treatment or the right dose during the first treatment
  • The flea medicine you used was either permeated or did not kill the flea eggs, which can bloom within 48 hours.
  • Your home or your cat’s bedding is infested with fleas

You should know that when you choose an oral flea treatment with Lufenuron for example, it should be combined with Pyrethrin spray for example to prevent the flea eggs and their larvae from continuing to develop, otherwise, your cat will quickly get fleas after 4 to 20 days after the oral flea treatment.

So what if the cat flea treatment didn’t work? 

In this case, I advise you to do two things:

1- Ask your veterinarian for advice

2- Brush your cat daily with a fine-toothed metal flea comb and give him a bath every week, you can even use natural repellents such as a mixture of water and lemon juice to prevent fleas from coming back on your cat until the next treatment and to avoid causing an overdose if you repeat an early flea treatment.

What to do in case of cat flea treatment overdose?

If you notice any signs that your cat is experiencing an overdose from the applied flea medicine, such as dizziness and uncontrolled tremors, remove the product from the cat’s back in case of topical treatment, give the cat 2 to 3 successive baths with liquid dish soap (with warm water) and take the cat to the nearest veterinarian or center.

What to do if your cat has licked some flea medicine?

If your cat has scratched itself after a topical flea treatment, it may end up with some of the active product in its mouth as soon as it starts licking its paw.

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Your cat will start to salivate and even get some foam at its mouth and may even become nauseated and vomit because of the bitter taste of the flea medicine, but this is not serious, you will now help him get rid of that bitter taste that has filled his mouth by encouraging it to have some water and food .

Give him a tasty snack or any wet food or canned tuna will help him get rid of the taste.

How long after flea treatment will cat stop scratching ?

After the flea treatment is applied, the fleas will start to move around and create an uncomfortable situation for your cat who will start to move around and scratch intensively.

This will depend on the treatment used, but your cat will stop scratching when the fleas stop moving and die, usually after 2 to 24 hours.

Do cat flea treatments kill their eggs and larvae ?

No. Oral flea medicine does not kill flea eggs because this type of treatment is only effective when the flea is drinking blood, and the young flea larvae will not die from this treatment because they usually feed on flea dirt after they hatch.

Topical flea medicine, on the other hand, will kill the adult fleas and prevent their eggs and larvae from developing as soon as they come in contact with the applied product, which will disperse itself all over the cat’s skin within 48 hours.

Should I put a cone or a shirt on my cat after flea treatment ?

No. You must first apply the product directly to the cat’s skin and in an area where the cat cannot lick it (on its shoulders).

If you have treated several cats at the same time and you want to prevent them from licking each other, you can put them in two different rooms until the product dries (after 2 hours).

Putting a cone on your cat is not necessary and the shirt, while it will keep the fleas from jumping off your cat, will make him more agitated because it will prevent him from scratching when the fleas start to get agitated shortly after the treatment.

Checking to see if the fleas haven’t caused or transmitted any disease to your cat

Unfortunately, fleas can transmit deadly diseases to cats, so few days after the flea treatment, once your cat’s condition has settled down, you will finally be able to find out if the fleas caused or transmitted any disease to your cat.

You can either take your cat to the veterinarian for a check-up or you can check for the following diseases that are usually caused by fleas yourself

Bartonella (fever lasting more than 3 days, vomiting, lethargy, red eyes, swollen lymph nodes, or decreased appetite)

Flea Allergy Dermatitis (FAD) whose symptoms are :

  • Skin inflammation and hair loss.
  • Scabs and crusted sores .
  • Darkening of affected skin.
  • Unpleasant odor .

Tapeworms in Cats whose symptoms are :

  • Shaggy coat.
  • Irritability.
  • Mild diarrhea.
  • Seizures.
  • Intestinal blockages

Anemia : the symptoms should be :

  • White gums
  • Lethargy
  • Your cat is sleeping more than usual

Final Thoughts

After flea treatment, cats react in different ways and the key is to be prepared to act if your cat shows signs of discomfort.

Be prepared to take your cat to the veterinarian in case of problems, prepare something for him to eat if he licks the product, and try to confine him to one room to prevent him from going outside and to know where to vacuum after the treatment to prevent flea eggs from falling into your carpet, hatching afterwards, and returning to infest your cat.

M Samy pet blogger and author at famillypet

About Author

Hey! Samy here , Welcome to my Blog I'm an animal lover, especially pets and Really concerned about their well being ; I've been around and caring for all my life and Now ; a full-time Pet blogger at your service . My motto here at Famillypet is: "Pets First" ... Read More