I have two cats, who i absolutley love and adore. I started noticing fleas on them. well i just wish now that i would have seen this websight before now because i never knew. I put the hartz on the back of their neck. My beautiful lilac siamese constantly licks and scratches and actually pulls little hunks of her hair out, it is from that hartz treatment. it also burned the hair on her neck where i put it. she seems so uncomfortable in her skin now.My other cat constantly scratches that place on his neck where i put the hartz. I cant believe the horrible state my cats are in because of that treatment.