E-liquid is the mixture used in electronic cigarettes. The main ingredients in the e-liquid usually are propylene glycol, glycerin, nicotine, and flavorings. However, there are e-liquids sold without propylene glycol, nicotine, or flavors. The liquid typically contains 95% propylene glycol and glycerin. Propylene glycol and glycerine are used to produce the vapor while the flavoring provides the taste and aroma.