<P> An electronic cigarette or e-cigarette is a handheld electronic device that simulates the feeling of tobacco smoking . It works by heating a liquid to generate an aerosol, commonly called a "vapor", that the user inhales . Using e-cigarettes is commonly referred to as vaping . The liquid in the e-cigarette, called e-liquid, or e-juice, is usually made of nicotine, propylene glycol, glycerine, and flavorings . Not all e-liquids contain nicotine . </P> <P> The health risks of e-cigarettes are uncertain . They are likely safer than tobacco cigarettes, but are of unclear effect in relation to other methods of stopping smoking . Their long - term health effects are not known . They may help some smokers quit . When used by non-smokers, e-cigarettes can lead to nicotine addiction, and there is concern that children could start smoking after using e-cigarettes . So far, no serious adverse effects have been reported in trials . Less serious adverse effects include throat and mouth irritation, vomiting, nausea, and coughing . </P>

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