PG and VG are both humectants, and yes they do make your tissues feel dry as a bone! If you don't drink enough H2O, your tissues can become so dry they crack open and become very sore and sometimes inflamed/and/or infected, especially in your nose and throat, not a good thing! AtomPunk is right on, you can't drink too much water ~ a couple liters every day. PG and VG are also very good anti-bacterial solutions, so with proper hydration and vaping you should be able to fight off colds etc. better. But your tissues were meant to be moist, and your lungs need to be moist enough to cleanse themselves, a plus if you are an EX-smoker, because with vaping you don't inhale tar anymore! H2O really helps in your re-hab.