Permethrin is a poison. I would never, ever expose my child or my pets to it.

Permethrin, like all synthetic pyrethroids, is a neurotoxin. Symptoms include tremors, incoordination, elevated body temperature, increased aggressive behavior, and disruption of learning. Laboratory tests suggest that permethrin is more acutely toxic to children than to adults. There are over 18 brands of permethrin spot-on products available that are labeled for "dogs only." These typically contain high concentrations (45-65%) of permethrin insecticide and are used for flea and tick control. These permethrin products have a good margin of safety when used on dogs, but even a few drops of concentrated permethrin could be lethal to a cat. Owners most commonly expose cats to these products through inappropriate or accidental application. The signs commonly seen with permethrin toxicity in cats include generalized tremors, muscle fasciculation and seizures. Signs can develop within hours or may be delayed up to 48 hours.