Why do some people get hangovers while other people dont?

Everybody does: The short answer is everybody does get one, it is just that it is expressed differently in different people. Some are more severe than others. It also matters how much you drank over what time, and what your other mood was. Also some people are going to deny they have the symptoms, and actually feel worse than they say they do.

Dehydration: A hangover is caused by dehydration, since alcohol is a diuretic. Some people will be better hydrated than others at the end of the festivities. You can help prevent a hangover if you drink plenty of water before going to bed after drinking.