The left side of the head hurts all the time, considering the possibility of functional headache, or it may be a typical migraine. If it is a migraine, the incidence of women is usually higher than men, and it often starts in young age, alternating between attack, relief, and re-attack, and the frequency of attack will be reduced after middle age, because the headache attack is easily triggered by poor sleep, labor, or mental stress factors. Some patients may have a migraine aura, which may be manifested as a flash of light or bending of the light, etc. Migraine attacks may be more intense, accompanied by nausea and vomiting, and the headache may reach its peak within one hour. Treatment is mainly symptomatic pain treatment, you can take oral Triptans to relieve headaches.