Breathing left chest pain may be related to lung disease, heart disease, costochondritis, fork in the road and so on. 1. Lung diseases: when lung diseases such as pneumonia, spontaneous pneumothorax, infectious pleurisy attack, because of inflammation stimulation and other reasons, it will lead to chest pain and discomfort, chest pain and discomfort in deep breathing, activity, often accompanied by coughing, coughing up sputum, fever and other symptoms. 2. Heart disease: such as angina pectoris, pericarditis and other diseases, this kind of cardiovascular disease attack will also lead to breathing in the chest pain, angina pectoris patients in rest or take nitroglycerin and other drugs will gradually relieve the pain, pericarditis patients because of inflammation stimulation and fibroplasia, there may be a persistent pain and discomfort in the left chest when breathing. 3. Costochondritis: mostly caused by non-infectious factors, chest pain and pressure pain, which can be manifested as pain in the middle of the chest, and redness, swelling, heat and pain in the local skin caused by infectious factors. The pain may radiate to the back of shoulder, armpit, neck and chest, and may be aggravated by deep breathing, activity or exertion. 4. Breathlessness: Breathlessness is mostly due to insufficient warm-up before exercise or over-exertion or improper exertion when engaging in physical labor, resulting in respiratory muscle spasm and pain. Rest, massage will generally be gradually relieved. It is recommended to go to the hospital in time when the symptoms of breathing left chest pain, identify the causes under the guidance of the doctor symptomatic, cause-specific treatment.