I just called and spoke with a consumer representative (1.800.223.0182) re: listerine pre-brush rinse. It was explained that the white peeling is due to the peroxide in the product bonding to the germs in your mouth. As for my black tongue, I was not given a reason for that, so I'm going to assume it's caused from the peroxide interacting with something you may have eaten (in my case, some purple tums).
