Flea treatment for two cats, including a kitten

A new kitten joining a home with an existing cat is a lovely milestone — but it does mean you need a flea plan that works safely for both animals at once, which takes a bit of thought. Before I get into anything specific, I want to flag the most important safety rule in cat flea treatment: permethrin and certain other insecticides that are fine for dogs are genuinely toxic to cats — even indirect contact with a treated dog can be dangerous — so we need to stay strictly within cat-safe products here. Can you tell me how much your Himalayan weighs, how old the incoming kitten will be when it arrives, and whether either cat has any current flea signs or if this is purely preventative?

Good that you're thinking ahead. Here's the important wrinkle: most licensed spot-on treatments aren't approved for kittens under 8 weeks, and some require the kitten to be at least 12 weeks or over 1kg before use. At 9 weeks and 800g, your new kitten is in a grey zone where the options narrow considerably. For your Himalayan at 5kg there's no issue — she can go on a standard monthly spot-on straight away. The product I'd recommend for both cats, once the kitten is ready, is Advantage (imidacloprid) by Bayer/Elanco. It's one of the few spot-ons with a licensed lower weight band that covers smaller kittens, it contains no permethrin, and it kills fleas on contact without needing them to bite — which matters with a longhaired Himalayan where flea dirt can hide easily.

Advantage for cats is licensed from 8 weeks and over 1kg. Your kitten is 9 weeks, which clears the age threshold, but at 800g she's just under the 1kg weight minimum. I'd hold off for a week or two, weigh her again once she's settled in, and apply it as soon as she hits 1kg — kittens at that age gain weight quickly so it usually isn't a long wait. In the meantime, treat your Himalayan with Advantage now to reduce the flea burden in the home before the kitten arrives, and that will give the kitten meaningful indirect protection straight away.

Yes, and especially before the kitten arrives. Up to 95% of the flea lifecycle — eggs, larvae, pupae — lives in the environment rather than on the cat. A household flea spray like Indorex Defence (which is safe to use around cats once dry) treats carpets, skirting boards and soft furnishings and gives residual protection for up to 12 months. Vacuum thoroughly before you spray to stimulate any dormant pupae into hatching, then apply the spray and let it dry fully before letting either cat back into the treated areas. Washing the kitten's new bedding on a hot cycle before she arrives is also worth doing. Treat the Himalayan with Advantage now, spray the house this week, and then you're in a really strong position when the kitten comes home.

Exactly right. Advantage for the Himalayan now — use the 4kg+ cat pipette given she's 5kg. Indorex for the house this week before the kitten arrives. Then Advantage for the kitten once she reaches 1kg, using the small cat/kitten pipette (up to 4kg). Both cats on monthly Advantage after that and you'll have a consistent, permethrin-free routine that's safe for the whole household.