The pain on the left side of the head may be caused by the following reasons: 1, neuropathic headache, the pain on the left side of the head may be caused by the trigeminal nerve, occipital nerve, etc. The pain is often related to mental tension, fatigue, lack of rest and the presence of infectious diseases, the pain can be examined by the hospital to identify the cause of symptomatic treatment. 2, the pain on the left side of the head may also be caused by cerebrovascular spasm. The pain is often related to cerebral vascular lesions, as well as the patient’s fatigue and lack of blood supply to the brain. 3, the pain on the left side of the head may also be suffering from a disease, such as lack of blood supply to the brain, suffering from cardiac arrhythmia and other causes of insufficient blood supply to the brain, can This can lead to throbbing pain in the brain.