You rub it into the carpet... not the cat! It kills the fleas at the base
of the carpet. If it weren't safe it wouldn't be recommended by our
veterinarian and marketed as a flea killer under the name of "Flea Busters".
It works. We have used it with absolutely no ill effects. When the fleas
are eradicated from the carpets then the ones in the cats fur eventually
diminish also, and no chemicals have been applied to the animal !!!