If you spin around and around, why is it that you can feel a little sick? The answer lies in how we sense our balance, and an ancient disease of the gut. We get our sense of balance in large part from the vestibular system of the inner ear. A delicate little set of organs in there contain fluid, and having a good sense of balance requires that these “fluid spaces” be properly maintained. However, our balance is, of course, also determined by what we see (try standing on one leg with your eyes closed).
When you spin around, the fluid in your inner ear gets sloshed around, momentarily confusing that sense of balance. Your eyes tell you you’re standing still, but your inner ear tells you you’re still spinning. Your brain panics when it gets this disconnect between the messages from your inner ear and your eyes. That’s because this is one of the signs of botulism poisoning. Botulism affects the inner ear and can result in this kind of disorientation. So what does the body want to do? Vomit, to get out that nasty toxin.
You can get the same effect if your eyes tell you you’re moving (for instance, walk into a room where the walls appear to move) but your inner ear tells you you’re standing still.