Smoking is harmful to the body and even two or three cigarettes a day can lead to an increased risk of developing cardiovascular and lung diseases. Tobacco contains many toxic substances. The main harmful components include nicotine, tar and carbon monoxide and other harmful substances. Even two or three cigarettes a day can damage the mucous membranes of the respiratory tract and easily induce cancer and other diseases. In addition, smoking can accelerate the process of pulmonary fibrosis, which may also induce pneumonia, bronchitis, chronic obstructive pulmonary disease, and may also induce cardiovascular and cerebrovascular diseases or malignant tumors. Smokers who cut down on smoking or choose to smoke fine cigarettes, low-tar cigarettes or herbal cigarettes will not reduce the risk of disease or gain health benefits. Quitting smoking is the only way to reduce the health risks of smoking. Two or three cigarettes a day can also be more harmful to the patient, so it is advisable to quit smoking as soon as possible for the sake of good health.