There are four basic ingredients in ejuice, propylene glycol, vegetable glycerin, flavoring and nicotine. Nicotine and flavoring account for about 8% to 10% of the total composition of e-juice. The rest of the liquid is propylene glycol (PG) and vegetable glycerin (VG).
As mentioned, three of the four ingredients in e-liquid are food grade substances. As for the nicotine in e-liquid, that is pharmaceutical grade and extracted from tobacco plants. Because the nicotine in vaping liquids is extracted from tobacco plants, the FDA has classified electronic cigarettes as a tobacco product. Nicotine is considered an addictive substance. E-liquid with nicotine is made for adult tobacco consumers only.