Do you get motion sickness? It might be because your body thinks you're being poisoned. This is why.
The human body is an amazing thing. Even when it doesn't seem like it. Motion sickness, for example, may seem like an unnecessary annoyance, but the body is really trying to protect you. It's just confused.
The brain's area postrema is responsible for inducing vomiting when poisons are detected. It also resolves conflicts between vision and balance.
When the body feels motion (e.g. On a boat) but doesn't see it (because the windows are covered, etc.), It assumes that there is something wrong.
Specifically, it believes the body is hallucinating and that poison is the source of this hallucination.
To rid the body of poison, it induces vomiting. So next time you get carsick or boatsick or any kind of motion sick, just remember that your body is trying to help you.