Some say "neurotoxin". Others say "neurotoxin till dried".
Frankly, I'll keep it away in any form. I dont want to harm my cats. Even if it means that I'm a human pincushion to mosquitoes and ticks.
They make flea collars for cats with permethrin (I found out just now) so it can’t be that toxic. If you’re really worried just get a pair of hiking pants and boots and keep them in a catproof tote.