The main harms of e-cigarettes to the human body include addiction, carcinogenesis, respiratory and digestive damage, and some other damages that have not yet been researched and clarified. 1. Addiction: E-cigarettes, like traditional cigarettes, contain addictive substances such as nicotine, which will make people who smoke e-cigarettes dependent on them and unable to quit. 2. Carcinogenic: E-cigarettes contain many carcinogenic substances, such as formaldehyde, nicotine, benzene, etc. Long-term smoking of e-cigarettes may increase the risk of various types of cancers in smokers. 3. Respiratory and digestive damage: E-cigarettes produce aerosols of unknown composition during smoking, which contain many kinds of irritating substances that can irritate the respiratory tract. In addition, in order to increase the attractiveness of e-cigarettes, merchants will add flavors and many other substances to produce different flavors of e-cigarettes, which will also have potential damage to the digestive system.