Why does the left side of the head ache?

The pain on the left side of the head may be caused by local trauma, and also related to personal mental stress or other diseases, such as cervical spondylosis and hypertension. If the head is hit by trauma, it will cause thrombosis and cause local pain. Long-term suffering from cervical spondylosis, the herniated disc will compress the vertebral artery, thus causing vertebral artery stenosis, which will affect the blood supply to the brain, thus causing transient ischemia and hypoxia in the brain, and also causing paresthesia in the head, showing pain symptoms. Long-term suffering from hypertension and other diseases will cause vascular damage, causing thrombosis in the blood vessels, causing pain after local compression.