PG or propylene glycol is an organic compound (a diol alcohol), usually a faintly sweet, odorless, and colorless clear viscous liquid that is hygroscopic and miscible with water and acetone. Propylene Glycol is recognized as generally safe for human consumption by the Food and Drug Administration. It is used in food coloring and flavorings. It's also used as an additive to keep food, medicines, and cosmetics moist, and in machines that simulate smoke (theatrical fog machines). Propylene glycol functions to provide the vapor mist that looks like smoke and to suspend flavor.
VG or vegetable glycerin is very similar to PG in that it has some of the same uses as PG. What's written above can be applied to VG. Although the vast majority of our customers notice little to no difference between the two, a small number of people find propylene glycol to be an irritant (sore throat, etc.) We launched our Red Oak of PG-free e-liquids so everyone is able to enjoy juices made by Johnson Creek. We pioneered PG-free e-liquids.