system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it that when you get a bad enough headache it can sometimes induce vomiting.
gpt
Sometimes the worst headaches are migraines, and migraines do more than just hurt your head. They also affect nerves all over your body, including the digestive system. It's possible to take a migraine abortive and not have your head hurt, but still have the headache in that the rest of your body feels screwed up.  Vomiting is one of the "other symptoms" of migraines other than pain.

I don't know about other headaches than migraines though.