So glad I searched and found this site because I put one on my two-year-old Shih Tzu within hours I noticed he got really sick. Lethargic not playing won’t drink won’t eat. I didn’t think nothing about it at first because my boyfriend has a habit of feeding him things he’s not supposed to. And then I decided to look up the side effects to his new flea collar because I cannot stand to watch him go through this. I did take it off immediately after reading some of these post thank you all so much for putting these on here.