I believe only the fumes are harmful. DRS, I don't believe it is the same kind of silicone that is used in breast augmentation. Daniel, if it bothers you, you can mix some water and alot of cayenne pepper and spread it on the sealant so it deters them from chewing. It's pretty funny when they go investigate what that new red stuff on the wall is. They get it in their nose and just go ballistic, poor little guys. I had to do that to one of my rat's water bottles when she kept chewing holes in them, neurotic little turd.