There are many causes of left side of the head pain, and the common causes are mainly the following: 1. Migraine. The disease is mainly manifested as one side of the head paroxysmal swelling pain, mostly accompanied by visual aura symptoms, with a sense of vascular pulsation, mostly seen in patients with high mental stress, overworked, taking drugs such as tianma headache tablets, blood clearing brain particles can improve the symptoms. 2, herpes zoster. The disease is due to herpes virus attack, mainly manifested as a side of the head cut-like or needle-like pain, pain symptoms are not more than neutral, the skin has a characteristic cluster of blistering rash, through antiviral and nerve nutrition treatment can relieve symptoms. 3, trigeminal neuralgia. The disease is due to nerve demyelination, mainly manifested as one side of the temple symptoms knife-like pain, the symptoms last for a few seconds to tens of seconds, usually no more than a minute, taking antiepileptic drugs such as carbamazepine, sodium valproate can be symptomatic treatment.