Flea treatment for thick-coated cats

A Norwegian Forest Cat's double coat is notoriously dense and water-repellent — it's actually designed to shed moisture, which is exactly why spot-on treatments struggle to penetrate and absorb properly on these cats. Before I suggest an alternative, one thing worth flagging first: cat flea treatment has a critical safety consideration that doesn't apply to dogs. Permethrin and several other insecticides that are perfectly safe for dogs are toxic to cats and can be fatal, so it's essential to only use products specifically licensed for cats. Now — your cat is 9 years old, which is helpful to know. Can you tell me roughly how much they weigh, whether you're dealing with an active infestation right now or looking for ongoing prevention, and have you treated the home as well as the cat?

That's a really common problem with Wegies and Maine Coons — the coat literally repels the product before it can reach the skin. At 7kg she's a large cat, so dosing matters too. Given that spot-ons are clearly not the right format for her coat type, I'd move away from them entirely and switch to the Seresto collar for cats. It's a slow-release collar that delivers flumethrin and imidacloprid continuously through the coat and skin without needing to absorb through that thick undercoat the way a liquid spot-on does. It works for up to 8 months, kills fleas and ticks, and is one of the few formats that genuinely suits double-coated breeds. Just confirm — is she an indoor-only cat, or does she go outside?

That makes the Seresto collar an even better fit. Because she's outdoors, she's going to keep re-encountering fleas, and the collar gives her continuous 8-month protection without you needing to remember monthly applications. It also repels as well as kills, which matters for a cat with outdoor access. One thing to make sure: get the cat-specific version, not the dog one — the dog collar contains permethrin and would be dangerous for her. The cat Seresto is clearly labelled and widely available on Amazon UK. Now, the home treatment is genuinely important here — roughly 95% of a flea infestation lives in the environment as eggs, larvae, and pupae rather than on the cat. If you don't treat the house, she'll keep getting reinfested regardless of what's on her. I'd pair the Seresto with an indorex or RIP Fleas household spray — one can covers an average home and also kills eggs and larvae.

It should be comfortable — it's a soft flexible collar, not rigid. Fit it so you can slide two fingers underneath, and trim any excess length after fitting. For an older cat, the main thing to watch in the first few days is any skin irritation at the contact points on the neck; a small amount of temporary hair thinning under the collar is normal and resolves on its own. If you see persistent redness, itching, or she seems distressed by it, take it off and speak to your vet. At 9 she's senior but that age alone doesn't contraindicate it — Seresto is suitable for cats from 10 weeks and there's no upper age limit. Because she's older it's also worth making sure she's had a recent general vet check if she hasn't recently, but that's separate from the flea treatment decision.

That combination should sort it. To recap: Seresto collar for cats (not dogs), fitted with two fingers of slack, paired with a household spray like Indorex covering all carpets, skirting boards, and soft furnishings. Wash her bedding on a hot wash at the same time. You should see the infestation come under control within a couple of weeks, though you may see the odd flea for up to a month as pupae hatch out — that's normal and doesn't mean the treatment isn't working.