I used Hartz One spot treatment that I bought at Wallgreens on my cat. She became very sick. She was acting like she was very scared. I noticed she wasn’t cleaning herself and she didn’t have any energy. I then noticed she wasn’t eating. I didn’t even think of the Flea treatment at first, I thought she just had a regular illness. After two full days of this I started getting concerned and started thinking about calling a Vet. I then realized the Flea treatment I had given her and I immediately gave her a bath. Almost right after the bath she seemed back to normal. She wasn’t scared and she was very hungry and started cleaning herself again. I wonder how many pets get sick from this Harts product and how many die?