The causes of constant left-sided headache are as follows: first, it is seen in patients with migraine, who mostly have recurrent headaches and relatively fixed pain sites, and are treated with non-steroidal anti-inflammatory drugs. Secondly, headaches on the left side are caused by increased intraocular pressure in the left eye, especially in patients with glaucoma, and intraocular pressure testing is performed when necessary. Then, the old left headache is also clinically seen in the headache caused by sinusitis, usually the patient has sinusitis of the left frontal sinus, butterfly sinus, septal sinus, after the cold leads to the left side of the headache. Finally, the left side of the headache can also be seen in the neuralgia left after herpes, for example, the patient has shingles on the left side of the head, especially diabetic patients will have posterior neuralgia, which is manifested as the left side of the headache.