I have used a calming collar on Noodles when she was over-grooming. It helped some; but the scent was pretty noticeable. I could tell when she walked up without seeing her. It was pleasant to me; but not to her. She ended up trying to groom it off so I just left it near where she liked to sleep. My concern would be putting one on an outdoor cat. The one we had was made like a flea collar; so it wasn't a break-away like a safety collar.