I work at a veterinary clinic we were told to try cheristin on our office cats. We did and it killed one of them! This medicine is EPA approved not FDA approved!! The Elanco Company first put this product on the shelves under the name Assurity and after numerous animal deaths they took if off the shelves and repackaged it under the name Cheristin. When I contacted Elanco and told them about the cat's death, they told me nothing like this has ever happened before, but i highly doubt that our clinic cat would of been the first to die from this!! The Elanco Company offered to pay for a autopsy and when i asked the autopsy doctor about the results he said it was CHERISTIN that killed her!! I have been doing as much research as possible and I highly suggest you do too!! There is no expiration date on the box! How is that even possible? There is no way it could last forever and not go bad. The main ingredient is Spinetoram, a pesticide used to kill insects on trees!! I want this to be known so no one will ever use Cheristin and have anymore animals die!! PLEASE only use a product that is FDA approved for all animals!! Elanco told me the incident with my office cat passing away would be reviewed and not much else would be done about it. I can not believe it. We love our office cat and would never want anyone else to go through this heartbreaking ordeal!!!