My cat of fifteen years old, beautiful hair and healthy died a couple months after putting a hartz flea collar on it, and it had a horrible reaction and lost hair. I took that off and treated it with the advanced spot. She tore her hair out till she was bald and got real skinny and boney and died. She ate the night before, used her litter and showed only the above. Then I found her. My beloved cat. Always used other flea preventive measures from the vet. when I worked, but since I retired Ithought I would save some money, and I did, but I lost my darling cat. Sure, you can get your few bucks back, but thank a lot Hartz.