The headache that appears the day after staying up late is mainly due to three conditions: 1. The patient has a history of chronic migraine, and the headache will appear after staying up late, triggering a migraine attack. 2. The brain cells are not fully rested so the headache appears, which is a normal physiological phenomenon. Everyone who stays up late often has headache symptoms. 3. Staying up late can cause headache symptoms due to elevated blood pressure, so it is recommended that patients go to the hospital to measure blood pressure and observe whether it is very high. In addition, it is recommended that patients do not stay up late often, which is harmful to health.