How long does it take for fleas to die after treatment?

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When you discover fleas on your pet, it’s only natural to want to get rid of the blood-sucking parasites as soon as possible. Not only are they causing your dog or cat discomfort, but they could lead to a dreaded flea infestation in your home.

How long does it take fleas to die?

The good news is that there are lots of products available that will help you get rid of the itchy pests. This guide gives you an idea of how quickly fleas die after treatment, and looks at other factors to consider when choosing a flea product, to help you decide on the right flea treatment for your pet.

How long does it take for flea treatments to work?

Fleas are pesky creatures. They are extremely mobile and reproduce rapidly, so taking back control and getting on top of the problem can take time, and often involves not just treating your pet, but also treating your home.

Flea control products for pets come in a variety of forms including spot-ons, flea collars, tablets and sprays. They use various different active ingredients to kill fleas, which means they all work slightly differently. The time it takes for products to kill fleas can therefore vary depending on the product used. 

Active ingredient imidacloprid is able to kill fleas through contact

Imidacloprid is an active ingredient present in several flea products - including Advantage spot-on and Seresto Flea and Tick Control collar. Imidacloprid spreads throughout your pet’s skin and coat, and is able to kill fleas through contact; this means that fleas don’t have to bite your pet to be killed.1 Other flea products, such as oral flea tablets and some spot-ons, are active in the bloodstream, which means fleas have to bite your pet to be affected. Reducing the chance of flea bites helps to protect your pet against the discomfort and irritation these pests can cause, and also helps limit the exposure to potential infections that can be carried by fleas.

Imidacloprid kills fleas within 24 hours. Along with imidacloprid, Seresto Flea and Tick Control collar also contains flumethrin, which repels and kills ticks. The collar works for 7-8 months, providing the longest-lasting flea and tick protection in a single application. 

Imidacloprid also kills flea larvae in the home environment, for example in carpets and pet bedding, helping to break the flea life cycle.

What about flea shampoos?

As well as the various options mentioned above, flea treatment can also come in the form of a flea shampoo, which is applied directly to your pet’s coat.

Although shampooing your dog or cat might feel like a reassuringly immediate solution for banishing fleas, it doesn’t offer long-term protection. Scrubbing your pet will only kill fleas on them at the time of bathing, so your pet will be at risk of re-infestation once the shampoo has been rinsed away. If you do want to use a shampoo, ideally follow this up with a longer-term preventative flea treatment.

Flea shampoos can kill fleas that are on your pet, but rarely have any residual activity

Treating your home

By the time you spot a flea on your pet, it’s likely that there are a couple of generations of new fleas in your home. That’s because the female flea can lay up to 50 eggs per day, and these eggs hatch into flea larvae in your home, burrowing into carpets, sofas, your pet’s bedding, and anywhere else in the home your pet goes. The larvae spin cocoons around themselves, and after a period of time these hatch into new fleas ready to bite your pet and start the cycle all over again. Treating your home, as well as your pet, is an important part of getting on top of a flea infestation. 

Vacuum carpets

  • Thoroughly vacuum all carpets and rugs in the house, paying close attention to the areas where your pet sleeps.
  • Be sure to empty the vacuum immediately afterwards and dispose of it outside of the house.

Wash all bedding

  • Remove sheets from beds in your household, cleaning them on a hot wash, to kill any fleas present.
  • You should also wash your pet’s bedding.
Remember to wash all bedding in your household on a hot wash to kill fleas

Use a household flea spray

Once you’ve cleaned your house, you will need to use a special flea treatment suitable for use within your home.

The most effective are veterinary approved household flea sprays. These handheld sprays enable you to pay particular attention to places flea eggs, larvae and pupae like to hide, such as under beds and furniture. Always follow the instructions on the can, and treat thoroughly, as fleas really can get anywhere within your home! The time it takes to remove fleas from your home will be dependent on the level of infestation you have. In some cases, it can take several months to get rid of them completely.

Remember to keep up with regular flea control to help stop them coming back! Seresto flea and tick control collar provides up to eight months of protection in a single application.  

I’ve treated my pet and my home, so why am I still finding fleas?

It’s frustrating to spot a flea jumping around on your pet, or flea dirt (flea faeces) in your pet’s coat, after the time and effort it has taken you to treat your pet and thoroughly de-flea your home. 

The main thing is to give it time. Once a flea infestation has set up in your home, it can take a while to completely clear it. The cocoon stage in the flea life cycle can remain dormant within your home for many months, so new fleas can continue to emerge for months, even after treatment. These fleas will quickly be killed after hatching if you have treated your home and kept up with regular flea treatment for your pet, but it can take a while for all the existing fleas to hatch and be killed.

It’s also worth remembering that no flea treatment forms a force-field to stop fleas from jumping onto your pets. But an effective treatment will quickly kill fleas once they have come into contact with your pet.    

Once you’ve got on top of an infestation, keeping up with regular flea treatment will help to make sure your pet and your home stay protected. Seresto Flea and Tick control collar protects your dog or cat against fleas and ticks for 7-8 months in a single application. 


  1. Mehlhorn et al. Parasitol Res (2001) 87:198-207, information is regarding mode of action and is not intended to relate to speed of kill or to imply parasites can be completely stopped from biting.

Find out more about Seresto Tick and Flea Control Collar

Pack shot of Seresto flea and tick control collars for dogs and cats

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