E-cigarettes are battery-operated products that turn nicotine and other chemicals into a vapor that is inhaled. They come in many different shapes, but each consists of a battery, a heating element, and a cartridge or tank to hold the liquid. The liquid itself is a combination of nicotine and flavorings suspended in propylene glycol, glycerin, or another fluid. An electric heating coil vaporizes the solution, and vapor (which looks like steam or smoke) is released through the mouthpiece. This is where the term “vaping” comes from.
It’s worth noting that there is no accepted definition of what an e-cigarette is, so manufacturers can change both the chemicals and how a device works and still call it an “e-cigarette.” In Europe and most countries, e-cigarettes are regulated like other products (such as pet food, children’s toys, or electronics). In the United States they are unregulated, perhaps the only product of any sort on the market today that has no oversight.
Medical review: Nathan Cobb, MD, September 12, 2017