We've had several cats come into the clinic due to toxic reation to the flea medicine. If you put anything on your cat and it start to shake, has rapid eye movement, or has a seizure bath it immediately and then take it to the vet. Yes bath it first so that less 'medicine' will enter the cats bloodstream. All the cats we've had have been fine. I"m sorry to hear about the loss of all your cats. I certainly don't recommend Hartz to anyone.