The left side of the back may have the following causes: first, herpes zoster, in the early stage of herpes zoster can appear on one side of the back pain, after the incubation period of 1-2 weeks can appear in groups of herpes, then to the dermatology department for early diagnosis and early treatment; second, intercostal neuralgia, when intercostal neuralgia can also appear on one side of the back pain, then to carry out early investigation, after the diagnosis Third, rib diseases, when there is a tumor or metastasis in the ribs, pain at the back of the ribs can occur, and CT and ECT examinations of the ribs should be performed for early diagnosis and early treatment; fourth, heart diseases, when there is a heart attack or angina pectoris, pain at the back of the left side can occur radiologically, and then a cardiac examination should be performed for early diagnosis and treatment. Heart examination for diagnosis and treatment.