PG, Propylene Glycol The ingredient in most eliquid recipes that produces vapor. Propylene Glycol, or PG, is on the FDA's list of substances generally recognized as safe, and is used in everything from fog machines to artificial flavors. Reduced PG, VG, Vegetable Glycerine A very small percentage of e-smokers have a sensitivity to PG. That's why we offer an alternative recipe. Our Reduced PG recipe uses Vegetable Glycerine as the main vapor-producing agent to create a similar vapor that is usually slightly thicker.