I just wanted to let you know my cat had a serious reaction to the Hartz 4 in 1 flea medication. I was unaware of the problems with Hartz products and purchased the flea medication. I applied the proper dose on my cat and within hours she bgan to scratch the medicated area and also had frequent tremors/shaking of her head and leg. She spent the next 2 days at the veterinarian getting medication and IV treatments. She is now home and seems to be fine. I am in the process of writing a letter to Hartz demanding reimbursment for both the vet bill and purchase price of the flea medication. I don’t understand how Hartz can continue to sell this medication when there are so many people who have had experiences similiar to mine. Thank you for getting this information out.