I used the Hartz Mountain advanced Care Flea and Tick Drops on my cat. Within 48 hours he became sick–he seemed weak and listless. As he didn’t improve in a few days, I took him to the vet and she examined him and treated him for fleas. The Hartz Mtn. Drops didn’t kill the fleas. He began to lose weight and became very listless. He wasn’t eating or drinking much water. I took him to the vet again. She found a tumor in his abdomen and stated that he would probably pass away in a week or two. He died 10 days later. I sent the documentation to Hartz as they requested. They refused to take responsibility for my cat’s death. To me it seems classic: a tumor as a result of a toxic substance. I wish I had known that it was not a safe product. Now, I am out $300+ For vet bills, which i requested that they pay. My Kitty was fine until i used those Hartz Mtn Drops on him. The worst of it of course, is that my beloved furry friend is gone. We miss him terribly. He was so friendly, affectionate and fun. He was a big furry tuxedo guy who was always looking for a lap to sit on or a cuddle from someone! He would answer us with meows — and of course was a great purring pal!