Left external chest pain may be related to trauma, chest wall disease, breast disease and other causes. 1. Trauma: generally caused by localized strains, trauma, bumps, long-term exercise, and history of exertion. 2. Chest wall diseases: such as costochondritis, which can be categorized into aseptic inflammation and purulent inflammation, and is usually manifested as limited pain with swelling. Intercostal neuralgia, often associated with viral infection, nerve compression, etc., typically manifested as radiating pain from the back to the chest, which may be manifested as left external chest pain. 3. Breast disease: often occurring in female patients, breast hyperplasia or breast growth caused by swelling, part of the paratesticular hyperplasia can also cause left external chest pain. Don’t smoke and drink; pay attention to keep warm, avoid cold and cold; pay attention to indoor ventilation, keep the air clean. There may be other causes of left external chest pain, such as spinal disorders, etc. It is recommended to go to the hospital in time to find out the cause of the disease, and give corresponding treatment and treatment under the guidance of the doctor.