system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Hangovers

I ask this one today for obvious reasons.

I have heard a lot of reasons as to what causes them, but I don't know what is real and what are just wive's tales.
gpt
Your body needs water to work properly. Not just that, it needs to move the water from one part of your body to another when needed, and it uses certain parts to process the water into a form it can use.

When you drink alcohol, it causes parts of your body which process and move water around to not work as well. Even though you might drink a lot of water (which you should, and it does help) your intoxicated body is slow to process it. In the meantime, it still needs to get that water from somewhere, and - here's the best part - so it takes water out of your brain. The headache you get is because your brain is shinking a little bit as the water is sucked out of it.