E-cigarettes may cause pneumonia. This is because the ingredients contained in them can damage the mucous membranes of the lungs and induce lung infections. E-cigarettes contain ingredients such as propylene glycol, glycerol, vitamin E acetate, etc., which, like ordinary cigarettes, can be addictive. Long-term smoking of e-cigarettes, the components contained in the particles will damage the mucosa of the respiratory tract, not only reduces the defense function of the mucosa of the respiratory tract, increasing the chances of infection by pathogens, but also able to affect the function of the gas exchange of the lungs, inducing lung infections. E-cigarettes can also lead to nebulized inhalation-associated pneumonia, which may cause respiratory failure in the short term, with serious consequences. Long-term smoking of e-cigarettes not only leads to pneumonia, but also increases the risk of lung cancer. Therefore, quitting smoking as early as possible is the best preventive measure.