Comparative study of lung toxicity of E cigarette ingredients to investigate E cigarette or vaping product associated lung injury ScienceDirect How to Understand Vaping's Dangers RSDC PG and VG are two common base ingredients in e liquids for electronic cigarettes, playing crucial roles in various vaping products. Let's explain their meanings using simple and understandable Ge Gou What's in an e liquid or vape juice? The main ingredients are propylene glycol (PG) and vegetable glycerine (VG). These are solvents that are basically used to dissolve and carry the other ingredients.