While this might be obvious, its a fact that when you vomit, its due to the vomit centre in your brain. While you might think that feeling sick and being sick are part of the same process, actually theyre not. While the act of vomiting has many triggers, once your vomit centre goes into action, theres nothing you can do but embrace it. This part of your brain eliminates anything that bothers the stomach's lining - excess food or drink, poisonous substances, bacteria, or viruses. Also interesting is the fact that if your inner ear canal is unbalanced, as happens during sailing and driving, the brain's vomit centre gets an alert. Hormone changes during early pregnancy also trigger the vomit response.