My mother recently used these flea drops on her cat. He is 19 years old & it nearly killed him! The drops started to make him sick. He couldn’t keep his food down or he just wouldn’t eat. H started to lose patches of hair & itch twice as much. Plus, he started having random seizures. My mother took him to the vet & was told to quit the flea drops immediately. He has almost recovered fully. He keeps having the random seizures every once in awhile. We nearly lost him because of these stupid drops. At his age, we were lucky that he could recover from this.