There are many reasons for headaches the day after drinking, including alcohol intolerance, elevated intracranial pressure, and sympathetic nerve excitation. 1. Alcohol intolerance: some patients have alcohol intolerance, once drinking, their liver due to the lack of ethanol dehydrogenase, can not quickly break down the alcohol, so that alcohol stays in the body for a long time -, the role of the cerebral blood vessels, so that cerebral vasodilatation, prone to cause headaches. 2. Elevated intracranial pressure: after drinking, alcohol tends to dilate cerebral blood vessels, accelerating blood flow, and the volume of blood vessels will also increase, potentially increasing intracranial pressure, causing headache reactions. 3. Sympathetic nerve excitation: if a large amount of alcohol, can make the sympathetic nerve excitation, the heart pumping volume increases, causing blood pressure rise, the brain blood pressure rises easily cause headache. If the patient’s headache after drinking is more serious and lasts for a longer period of time, he should consult a doctor in time and cooperate with the doctor to carry out targeted treatment, so as to avoid the occurrence of alcohol poisoning, which affects the health of the body.