Grannick's Bitter Apple spray is a taste deterrent for pets that chew things. I originally tried it when our bunny, Benny, was a baby and we were teaching him not to chew wires and furniture. The idea is that you spray something you want him to stop chewing and the next time he tries he'll end up with a nasty taste in his mouth. So the next time he thinks about trying to chew that item he'll remember how bad it tasted and that will stop him.
I found that not only did it work very well with the bunny, but it can also be helpful when you have a pet that chews itself. When our puppy, Sky, was little she had a rash and wouldn't stop licking and chewing it. We sprayed the spot with the Bitter Apple, after the vet said it was safe to, and it helped her to stop the chewing so the area could heal.
I've never found any damage to furniture from using the spray and it really saved it from from Benny the Bunny.