What is this nasty film on the inside of my cheeks and gums after I use mouth wash?

After I use mouth wash, there is a white film-like substance that will come off when I put pressure against the inside of my cheeks or gums. It will roll up into little balls and is somewhat gooey. This only happens after I use mouth wash, nothing else. What is this and how can I stop it? The mouthwash I use is Listerine Cool Mint. Thanks!|||Many mouth washes are very strong and make your mouth tissue slough off. Dilute it in water before using. some toothpastes can do this too.