Headache and nausea are very common symptoms the day after drinking alcohol. The main component of alcohol is ethanol, which will cause damage to the stomach and intestinal wall after entering the stomach, so the next day there will be nausea, vomiting and other gastrointestinal symptoms, which is very understandable. 2. After alcohol enters the body, acetaldehyde is produced by metabolism. Almost everyone knows that acetaldehyde is toxic, and some patients may lack the enzyme to metabolize acetaldehyde, causing a large amount of acetaldehyde to gather in the body, so they will have headache symptoms. Such patients are not recommended to drink alcohol because they are intolerant to alcohol and will have headaches and dizziness as soon as they drink.