Flea treatment for three cats — one product

A three-cat household where you want one consistent product — that's a very sensible approach, and it's actually easier to manage than mixing treatments. Before I get into recommendations, one thing worth flagging upfront: cat flea treatment has a critical safety consideration that doesn't apply to dogs — permethrin and certain other insecticides that are perfectly safe for dogs are toxic to cats, sometimes fatally so. Since all three of your cats share the same space, this matters even if you never plan to treat a dog. To point you to the right product, can you tell me roughly how much each of your cats weighs, whether you're dealing with an active infestation right now or looking at ongoing prevention, and have you treated the home as well as the cats?

Got it — all three in the treatment weight range for a standard adult cat product, which makes this straightforward. For a consistent spot-on you can use across all three, I'd go with Advantage 80 by Bayer. It's imidacloprid-based, has no permethrin, and is specifically licensed for cats. It kills adult fleas within 24 hours and has some larval activity too. One pipette per cat, applied to the back of the neck. It's not prescription-only, so you can order it directly. Given you have an active infestation across all three cats, I'd treat all of them on the same day — staggering it just lets fleas keep cycling between them.

Quite urgent, honestly. About 95% of a flea infestation lives in the environment — eggs, larvae, and pupae in carpets, sofas, and bedding — not on the cats themselves. If you treat the cats but not the home, the fleas will just reinfest them within days. I'd use Indorex Defence Household Flea Spray — it's the most widely recommended household spray in the UK for a reason. It kills adult fleas on contact and contains an insect growth regulator that stops eggs and larvae developing for up to 12 months. One 500ml can covers roughly 75 square metres. Vacuum thoroughly before you spray, leave the rooms empty for a couple of hours after, and keep the cats out until everything is dry.

Every four weeks to maintain protection. Once you've cleared the infestation and treated the home with Indorex, you could reassess whether you want to continue monthly year-round or just through spring and summer when flea pressure is highest — but if any of the cats go outdoors, monthly all year round is the safer habit. Buying a three-pack per cat works out cheaper per pipette and means you're not scrambling when it runs out.