I used Hartz ultra gurad pro flea and tick drops on my cat Jett and it made her very sick. We put the drops on her on Sunday and noticed her going downhill over the next couple of days. By Wednesday she really wasn’t acting like herself so I called the vet. They said that the Hartz brand meds can be very toxic to cats. If so, I don’t understand why it is ok to sell these poisonous products. Unlike a lot of the stories that I read on this site, my cat is going to recover. I am very grateful and my heart goes out to all the pet owners who no longer have their pets due to Hartz. My cat had to have blood tests plus she was given a bath and fluids. My poor baby, I couldn’t afford Advantage which is why I bought the Hartz. What a huge mistake. Nothing but the best from now on for my old buddy Jett.