Different people have different images of what it is to mouth tape during sleep. Those that are abhorred by it might envision a big strip of duck tape over someone's mouth. Alas, the tape recommended is 3M paper tape for sensitive skin and the size of a postage stamp. It took some getting used to but I find I sleep better with the tape on. I cannot say one way or another if it makes a difference in morning phlegm. There are so many other variables.