Vet-recommended flea treatment for cats and dogs

Sounds like your vet has given you good advice — when one pet brings fleas in, the whole household needs treating or you'll just keep passing them around. Before we go further, one thing that's really important with cats: permethrin and several other insecticides that are perfectly safe for dogs are genuinely toxic to cats, sometimes fatally so. That means you cannot use the same spot-on product on both animals, and you need to be careful that any dog treatment you apply doesn't get onto your cat while it's still wet. With that in mind — how heavy is your American Shorthair, and what product is your vet or you planning to use on the dog?

Good news — Advocate for dogs contains imidacloprid and moxidectin, neither of which is the permethrin family, so that's a safe choice on the dog side. Your cat just needs her own separate product. Given she's 4.5kg and this is an active infestation the vet has flagged, I'd go with Advantage for cats — specifically the Advantage 80 spot-on for cats over 4kg. It uses imidacloprid, the same active ingredient as the dog's Advocate, which means no cross-contamination risk if they're in contact. It kills fleas on the cat within 24 hours and keeps working for a month.

Yes, Advantage is available over the counter — you can order it directly from Amazon UK without a prescription. It's a well-established product and widely trusted for exactly this kind of multi-pet household situation. Just make sure you pick up Advantage 80, which is the correct strength for a cat over 4kg like yours.

Definitely treat the house — around 95% of a flea infestation lives in the environment as eggs, larvae, and pupae rather than on your pets, so skipping it means the problem will return quickly. For the home, Indorex Defence Household Flea Spray is the one I'd recommend. It contains permethrin for the environment (where it's perfectly safe to use, away from your cat), plus an insect growth regulator that stops larvae developing. Spray carpets, soft furnishings, and the base of skirting boards, let it dry fully before letting your cat back in, and it provides protection for up to 12 months.

That's exactly the right combination. One last tip: wash your cat's bedding on a hot cycle before or just after you spray, and vacuum thoroughly first — that gets rid of a lot of eggs and larvae and makes the spray more effective. You should see a big improvement within a week or two.