Are Flea Treatments Dangerous for Cats?
7 July 2026
5 min read
Flea treatments save cats from parasites — but the wrong product can cause seizures and death. Dog flea treatments are toxic to cats when they contain permethrin.
Permethrin is lethal to cats
Never apply dog-only flea spot-ons to cats. Even contact with a recently treated dog can cause toxicity in sensitive cats.
How permethrin poisoning happens
- Applying dog flea treatment to a cat by mistake
- Using the wrong product from a multi-pet household stash
- Sleeping against a dog recently treated with permethrin
- 'Natural' dog flea powders containing pyrethrins
Symptoms — treat as emergency
Tremors, twitching, drooling, vomiting, and seizures can develop within hours. Wash off topical products only if your vet advises — wrong washing can worsen absorption. Go to emergency care immediately.
Know the symptoms
Review our full cat poisoning symptoms guide so you recognise neurological signs early.