Keep cats safe: never use dog flea products on cats
Important: some dog flea treatments contain permethrin, which is highly toxic to cats and can be fatal. Only use products labelled for cats on cats, and keep cats away from recently treated dogs as the label directs. If you think your cat has been exposed, contact a vet straight away.
Prescription vs over-the-counter
- Prescription treatments are often broader, covering several parasites in one product (such as fleas, ticks and worms, or heartworm in the US). Your vet needs to examine your pet to prescribe them.
- Over-the-counter treatments from pet shops and supermarkets can work well for specific parasites. Check the active ingredient, the weight band and what it covers.
Which parasites matter where you live
- Fleas are common everywhere. Most of the flea life cycle happens in the home, so treat all pets in the household and wash bedding.
- Ticks can spread diseases such as Lyme disease. Check your pet after walks in long grass or woodland.
- Lungworm (UK and parts of Europe) is spread by slugs and snails. Not every wormer covers it.
- Heartworm (much of the US and southern Europe) is spread by mosquitoes. Prevention needs a vet prescription in the US.
How to pay less for prescriptions
- Ask for a written prescription. In the UK, vets must provide one if you ask, though they may charge for it. You can then compare prices at online vet pharmacies.
- Vet health plans: many practices offer a monthly plan covering parasite treatments, vaccinations and check-ups. Compare the yearly total with buying separately.
- Buy the right weight band and multi-dose packs if your pet will stay in that band.
- Only buy from registered pharmacies and retailers. Very cheap “imported” products may be fake.
Last updated: 13 October 2026
