i was putting the drops on my cats neck. i have two cats. about a day later,i noticed large clumps of hair laying around my house. the cats shed alot so i didnt think it was something to worry about. i noticed my black cat,mr bebe scratching his neck alot and i saw the amount of hair that was falling off. i looked and he had a patch of skin showing the size of a half doller and his nose was very hot. i took him to the vet, they gave him a shot and some antibiotics. the vet asked me what i had put on him. i told the vet i put the hartz flea drops on him. the vet informed me that earlier a woman had brought her cat in and the cat had died. the woman had been putting the drops on her cat.my vet told me not to use the hartz flea drops. ive used advantage or front line ever since. this happened a year ago. i had no idea that the drops were making so many animals sick.