Flea treatment for cats: vet-confirmed infestation

Good news that your vet has already confirmed the infestation — that takes the guesswork out of it. Before we go further, one thing worth flagging: cat flea treatment has a critical safety consideration that doesn't apply to dogs. Permethrin and certain other insecticides found in many dog flea products are highly toxic to cats — even small accidental exposures can be fatal — so it's essential we only look at products specifically formulated for cats. Can you tell me how old and how heavy your cat is, whether this is an active infestation or prevention, and have you treated your home yet?

Perfect, that's really helpful. At 4.2kg and 5 years old she's a healthy adult cat, which gives us good options. Since the vet confirmed live fleas, you need something that kills the existing infestation fast rather than just a preventative. Did your vet specifically say to pick something up from a shop, or did they also mention any particular active ingredient they wanted you to use?

In that case, my clear recommendation is Advantage 80 for cats — it's the 4kg+ version, which is exactly right for her weight. It uses imidacloprid as its active ingredient, which is completely safe for cats and kills adult fleas on contact within 24 hours without needing to bite her. It's a spot-on you apply to the back of the neck, and a single pipette covers her for a month. It's widely trusted, vet-used, and importantly contains no permethrin whatsoever. You can find it on Amazon UK easily. One thing to do alongside this: you'll also want to treat your home, because up to 95% of a flea infestation lives in the environment — eggs and larvae in carpets and soft furnishings — not on the cat herself.

For the home, Indorex Defence Household Flea Spray is the one I'd recommend — it's the product most often used by vets and pest controllers, and it treats the environment for up to 12 months. Spray it on carpets, skirting boards, soft furnishings and under furniture, then vacuum after a few hours. Keep your cat out of treated rooms until the spray has dried. Together, Advantage 80 on your cat and Indorex in the home is a proper two-pronged approach that will clear this completely rather than just temporarily reducing numbers.

You should notice a significant reduction in fleas on your cat within 24 hours of applying Advantage 80. However, don't be alarmed if you still see the odd flea jumping around for a week or two after treating the home — that's normal, as new adults can hatch from pupae in carpets for several weeks even after treatment. As long as you've treated both your cat and the home, those newly hatched fleas will die quickly once they contact your cat. If she's still scratching heavily after two weeks, it's worth a follow-up call to your vet, but in most cases this combination clears things up reliably.