The headache the next day after crying at night is mainly due to the fact that during crying the patient has nasal discharge, which is mainly derived from cerebrospinal fluid. The outflow of nasal mucus when crying will reduce the volume of cerebrospinal fluid, and the patient does not have timely hydration to replenish cerebrospinal fluid production. Sleeping overnight will show some decrease in intracranial pressure, which is manifested as dull pain and tightness, and also accompanied by the feeling of unclear brain, which are all manifestations of low cranial pressure headache. Patients are advised to drink more warm water to replenish cerebrospinal fluid production, and the headache symptoms will be relieved naturally.