The main reasons why patients have headaches after drinking alcohol are the following: 1. Drinking alcohol stimulates the patient’s blood vessels causing excessive expansion of the blood vessels in the head, which can cause the patient to have headaches. 2. The ingredients in alcohol cause some stimulation to the nerves in the brain and to the meninges and fascia of the head, which can also cause the patient to have headaches. 3. The patient’s headache after drinking alcohol is related to the fluctuation of blood pressure caused by alcohol, because the increase in the alcohol content in the blood can cause a sharp increase in the patient’s blood pressure when drinking alcohol. The increase of alcohol content in the blood will cause a sharp increase in the patient’s blood pressure, which will also easily lead to spasms in the cerebral blood vessels of the patient, causing the patient to have headache symptoms. Therefore, if patients often have headaches after drinking alcohol, it is recommended that they avoid drinking alcohol to avoid cerebrovascular accidents due to blood pressure fluctuations caused by heavy alcohol consumption.