I bought one of Hartz’s flea and tick collars for my Morgan — a beautiful black cat with whie whiskers. Within a couple of days she developed a very ugly rash on her neck. It was all read and oozing puss. I noticed when she was constantly scratching her neck When I saw the rash, I just about died. I immediatly took the collar off and called my vet. He had me bring her in immediatly to his office. It was after hours for him, but when I told him about the collar, it was like he KNEW. He met me at the office and had to shave Morgan’s neck to get a closer look at the rash. Luckily for me, he said that she had a mild case. All I needed was some antibiotic cream after he gave her a shot. Within a week, she was looking better. When I wrote to Hartz about this, I never got a response. I will never use their products again!