Smoking e-cigarettes may be harmful to the nervous system, digestive system, and respiratory system. 1. Nervous system: E-cigarettes contain nicotine, which will stimulate the brain to release dopamine and produce the illusion of mental relaxation. Long-term smoking will not only cause patients to become dependent on nicotine, but also lead to varying degrees of decline in language, memory and sensory abilities. 2. Digestive system: When smoke is generated, alkaloids and other chemicals will be released. These alkaloids and chemicals may have toxic effects on the human digestive system, and adverse reactions such as nausea and vomiting, and burning in the stomach may occur. 3. Respiratory system: When nicotine is inhaled, it passes through the nose, throat and lungs, which can induce respiratory diseases, such as diffuse alveolar hemorrhage and other lung diseases, and may cause coughing, dry throat and other symptoms. It is recommended to quit e-cigarettes as soon as possible to avoid harm to the body. When patients experience nausea and vomiting as well as coughing and other symptoms, it is recommended to go to the hospital for examination and treatment under the guidance of the doctor.