Flea treatment for 5 cats in a house outbreak

A whole-house flea outbreak with five cats is genuinely tough to get on top of — so let's work through this properly. Before anything else, the most important safety note with cats: permethrin and some related insecticides that are fine for dogs are toxic to cats, and using the wrong product can be fatal, so we need to make sure everything in the house is cat-safe too. Can you tell me roughly how much your Manx and the other cats weigh, whether any of them are currently on a flea treatment already, and have you treated the home itself yet — carpets, sofas, skirting boards?

Right, so you've got an active infestation on all five cats and an untreated environment — that means eggs, larvae and pupae are already deep in your carpets and soft furnishings. Treating the cats alone won't crack this; about 95% of the flea population is off the animal at any one time. You need to hit both simultaneously. What's the living situation like — mostly carpeted, or hard floors? And are there any dogs in the house, or strictly cats only?

That's actually a manageable setup. Here's what I'd recommend. For all five cats, use Advantage 80 spot-on (the 80mg version, which covers cats over 4kg — for the ones under 4kg use Advantage 40 instead). It's imidacloprid-based, kills adult fleas within 24 hours, is completely permethrin-free, and is genuinely one of the most reliable over-the-counter options for cats. Apply it to the back of the neck where they can't lick it. For the house, use Indorex Defence Household Flea Spray — it's the gold standard for home treatment, contains permethrin for the environment but that's fine as long as cats stay out of treated rooms until surfaces are fully dry (usually a couple of hours). It also contains an insect growth regulator that stops eggs and larvae developing for up to 12 months. Vacuum thoroughly before spraying, focus on carpets, the rug, skirting boards and under furniture. You'll likely need two cans for your size of home.

You'll want to repeat it monthly for at least three months — that's how long it takes to fully break the flea lifecycle even after a good home treatment. New adult fleas will keep emerging from pupae in the environment for weeks, and they'll jump onto the cats, so keeping that barrier in place is what finishes the job. After three months, if the cats go outside, a monthly routine is worth keeping up. If they become fully indoor-only, you can reassess, but honestly for five cats it's a low-cost insurance policy.

Yes, Advantage is safe for older cats — age itself isn't a contraindication. The only caveat would be if she has a known health condition or is on other medications, in which case a quick word with your vet before applying wouldn't hurt. But for a healthy senior cat, it's one of the gentler options precisely because it works on contact rather than being absorbed systemically into the bloodstream the way some prescription treatments are. You're fine to use it on her alongside the others.