E-cigarette heats liquid nicotine electronically, so that liquid nicotine volatilizes into the body to produce smoking effect. But after nicotine is heated, there will still be some harmful substances. The main hazard is that the body will have the risk of cancer, especially if the body has lung-related diseases. If you smoke e-cigarettes regularly, there is a risk of decreased lung function and may also lead to bronchial asthma attacks.