Vape Juice Ingredients: All You Need to Know E liquid composition Vaping Post Does Vape Juice Expire? How to Tell, Shelf Life, & Storage 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. Do you know what you're vaping? Propylene glycol (PG) and vegetable glycerin (VG) are the main liquids in vapes. When heated, these chemicals turn toxic and aren't safe to breathe.