Ew, mine does that too, I just wipe it off. I think it's the metal reacting to something in the toothpaste. Which is stupid, they should be using some kind of BPA free plastic by now, it's 2012
You know you're old if you remember your toothpaste in a metal tube. It used to be a big argument at my house when someone would squeeze it from the middle, because it WAS a problem with those metal tubes
SO funny