Flea shampoo failed? What actually works for cats

If supermarket flea shampoo has failed more than once this summer, that's a really common pattern — and there's a clear reason it happens. Before I get into that, there's one safety point that matters a lot with cats specifically: products containing permethrin or certain other insecticides that are fine for dogs are toxic to cats and can be fatal, so it's important you only ever use products labelled specifically for cats. Now — how old is your cat and roughly how much do they weigh? And is the shampoo the only thing you've tried, or have you treated the home at all?

That explains a lot, actually. Flea shampoos only kill the fleas on the cat at the moment of the bath — they have no lasting effect, and they do nothing for the eggs, larvae, and pupae in your carpets and soft furnishings. At any point in an infestation, roughly 95% of the flea population is in the environment, not on the cat. So you've been treating the 5% and leaving the 95% untouched, which is why she keeps getting reinfested. At her age and weight there's nothing concerning about using a proper spot-on. Can I ask — has she ever had a spot-on treatment before, or has it always been shampoo?

For a healthy 7-year-old cat at 4.5kg, I'd go with Advantage 80 spot-on for cats. It's imidacloprid-based — no permethrin, completely safe for cats — and it kills adult fleas within 24 hours and keeps working for four weeks. It's well-established, widely used by vets, and available over the counter. You apply a small amount to the back of the neck where she can't lick it, and that's it. The critical thing now, though, is also treating the home. Indorex Defence Household Flea Spray is the one I'd pair it with — it contains both an adulticide and an insect growth regulator that stops eggs and larvae developing. Spray it on carpets, skirting boards, under furniture, and any soft furnishings, let it dry, and it provides protection for up to 12 months. Without doing the home treatment, the Advantage alone will help but she'll likely keep picking up new fleas.

Yes, that's fine. The whole point of applying it to the scruff of the neck is that it's out of reach for self-grooming. Even if another pet in the house gave the area a brief lick, the amount involved would be minimal and imidacloprid at that level isn't a concern for cats. Just part the fur, apply directly to the skin rather than the coat, and let it dry. Avoid bathing or getting her wet for 48 hours after application so it has time to spread through the skin's oils fully.

Treat her monthly for at least three months running. Given how long this infestation has been going, there will be pupae in the environment that can hatch over the coming weeks — they're the hardest stage to kill because the cocoon is impervious to most insecticides. Monthly Advantage means any newly hatched flea that jumps on her is killed before it can lay eggs. After three months, if the home is clear and you're not seeing any signs, you can reassess. But don't stop after one application thinking it's done — that's where a lot of people get caught out.