Around sporadically so I just saw this.
BethAnn, the reason you need to up your fluid intake while vaping is that the PG and VG and the typical sweetener (sorbitol) used in e-juices are all humectants. They absorb water from the atmosphere. In this case that atmosphere is your mouth, throat, lungs, and other mucus membranes. Basically you are the source of a lot of the vapor you exhale. That's not so bad if you only vaped for a minute or two, but the more you vape the more moisture you lose. Used in hand lotions in humidity conditions of less than 65%, VG actually pulls moisture directly out of the lower layers of skin and into itself, giving the allusion that the top layer of skin has been hydrated. Oh, and here's a fun fact for you, VG left out in the open can actually absorb it's own weight in water over the course of 3 days.