We had a cat who developed chronic kidney failure after putting Hartz topical flea medicine. Not only did he get burned and lose some of his fur, but he started getting sick. We were able to get him to bounce back three times, but the fourth he was too far gone and he died at home. I will NEVER use Hartz anything on any animal! I now have a 6 month old kitten and I use Frontline Plus for her. Hartz isn’t even recommended by vets.