My husband and I had to put our 5 year-old cat to sleep 2 days ago because of Hartz One Spot Flea Treatment, which caused her liver to inflame, acute hepatitis, and eventually, liver failure, for which nothing else could be done. We had gone to Wal-mart to try to purchase what we normally use (Advantage), but they didn’t have it, and we only saw two alternatives (Hartz and Sergent’s); we’ve used Seargent’s before, and it didn’t work, so we decided to try Hartz. We applied it to both of our cats, the other of which was not affected, but Aphrodite, about 12 hours later, was vomiting, not eating or drinking, and became very depressed and anti-social. So, we took her to the animal hospital after giving her a couple days to see if she would get better on her own (I also bathed her right after I first noticed the sickness.). After testing, the vet said Hartz caused her sickness, and eventual death. The vet put her on an IV to flush out the poison, and to nurish her, then prescribed an antibiotic, which seemed to help. However, she remained anorexic, never wanting to eat or drink anything, for if she did, she just threw it back up. She was still very weak, and kept to herself. She never recovered, so we took her back and found out it had turned into liver failure, so there was nothing else to do if she could not digest food. They (the vet) have seen cases like this, but outside of refunding us the $5 we paid for the product, Hartz refused to pay a dime. I can not believe this!