Why is a dog product deadly to cats?
Cats lack the liver enzyme that breaks down permethrin, so even a lick from a dog that was just treated can cause severe tremors and seizures within hours. High-strength "spot-on" products (45%+) are the most dangerous.
Why speed matters
Delaying care significantly worsens outcomes. Some signs appear hours or days later, so "looks fine right now" is not a reason to wait.
Signs to watch for
- Tremors or twitching, especially of the face and ears
- Excessive drooling, vomiting
- Twitching that becomes full seizures
- Wobbliness, jumping or over-reacting to noise
- High body temperature, collapse
What to do right now
- Call your vet immediately. Permethrin toxicity needs urgent veterinary treatment.
- Wash the cat with warm water and a small amount of dish soap to remove any product still on the fur.
- Keep the cat in a dark, quiet room — noise triggers seizures.
- Do NOT use dog flea products on cats, ever. Check the label for "permethrin" before use.
If your pet shows any of the signs above, go to the nearest emergency vet now and call ahead.
The step-by-step response, from the first minute to the vet visit, is in our Permethrin Toxicity in Cats emergency guide.