What Ingredients Are In An E Liquid? Nicotine, propylene glycol, sweet flavorings, and various toxic chemicals like carcinogens and heavy metals are found in vape juice, posing health risks, especially to youth. What Are the Ingredients of Vape Juice? 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.