A hangover is an unpleasant, but harmless condition that commonly happens a few hours after drinking beer or alcohol. Most people may have dizziness, nausea, vomiting, or headaches. These effects may last for a few hours or even a few days. Hangovers tend to happen after heavy use of alcoholic drinks. However, you may have symptoms just after having 1 or 2 portions the night before. Some individuals, on the other hand, may not have a hangover no matter how much alcohol they consume. Scientists have not fully understood about these differences, which are not linked to alcohol tolerance or resilience.