Common causes of left axillary pain include lymphadenitis, pleurisy, breast disease, coronary heart disease and so on. 1. Lymphadenitis, because the axillary lymph nodes are more abundant, when there are infections and other triggers, the axillary lymph nodes reactive hyperplasia, can appear axillary pain. 2. Pleurisy is an inflammation that occurs in the pleural cavity of the human body, caused by infections, malignant tumors and other causes, often manifested as chest pain, but also may appear under the armpit pain, may be accompanied by coughing and coughing, dyspnea and other symptoms. 3. Breast diseases, such as breast hyperplasia, suppurative infections, breast cancer, etc., because inflammation stimulates the lymph nodes to reactive hyperplasia, may appear underarm pain. 4. Coronary heart disease, due to coronary artery atherosclerosis leading to myocardial ischemia and necrosis, can also appear underarm pain, pain is mostly colic-based, can be accompanied by conscious heartbeat, shortness of breath and other symptoms. Causes of left armpit pain is more, may also be related to cellulitis, malignant tumors and other diseases, if the symptoms continue to be unrelieved, it is recommended to consult a doctor in a timely manner, to clarify the cause of the disease, targeted treatment.