Generally, e-liquid is made up of four basic ingredients; water, nicotine, flavorings, and propylene glycol or vegetable glycerin base. As a smoking lover, you have to be careful about the chemicals used in vape e-liquids. In a study, it is found that vaping exposes users to around 2,000 chemicals, including potentially harmful industrial compounds whether it is a popular brand. Go through the given link for more information.