The left back pain in men may have the following causes: 1. herpes zoster, the early stage of herpes zoster can appear on one side of the waist pain, after the incubation period can appear in groups of herpes, then to the dermatology department for consultation and treatment. 2. intercostal neuralgia, intercostal neuralgia can appear on one side of the waist hidden pain, radiating pain or pins and needles-like pain, then to be treated with nerve-nourishing drugs and local closure therapy. 3. 3, lumbar muscle strain, lumbar muscle strain may appear in patients who use one side of the waist for long-term work. 4, acute lumbar sprain, when there is an acute lumbar sprain, when there is a local lumbar sprain, there will be acute injury to the lumbar muscles, resulting in pain on one side of the waist. 5, kidney disease, when the kidney tumor, inflammation or cysts, stones can appear on one side of the back pain. In this case, CT, ultrasound and urinalysis of the kidney should be performed for diagnosis.