Why does my head spin when I’m drunk?

We’ve all been there: at the end of a long night on the town, you hit the sack and shut your eyes, only to find that the room seems to be spinning uncontrollably. It’s an unfortunate and expected side effect of heavy drinking, but why does this happen?

Although hangovers have been with us for centuries—mentions of them appear in ancient Egyptian and Greek artifacts and writings—scientists are still unsure what causes the condition. Indeed, some researchers prefer to leave the mysteries of the hangover in the dark, as they figure the unpleasant hangover experience will deter some from excessive drinking. For those of us suffering spinning heads, there’s similarly no sure answer, though science can lend some insight on likely causes.

Contrary to intuition, that spinning head feeling all starts in the ear. Besides hearing, ears are also responsible for helping with balance. If you took an anatomy course in high school or college, you may recall an appendage within the ear composed of three intertwined tubes—the semicircular canals, which may conjure up images of the infamous chestburster from “Alien” or conversely an elegant abstraction from a Klimt painting.

From within the semicircular canals and their neighboring olfactory appendages, balance can be maintained or thrown terribly awry. When your body moves, tiny hairs attached to jelly-like blobs within the semicircular canal also move. When these hairs bend with gravity, they send an electric signal to an attached nerve that in turn fires the signal to the brain and creates the sensation of motion.

Alcohol throws off this delicate balance, wreaking havoc on the finely scaled inner workings of the ear. When alcohol hits the blood stream it is transported all over the body, including to the ear. Blood laced with alcohol has a different density than its teetotaling counterpart and thus distorts the shape of the inner ear. The swollen ear parts push on the tiny sensory hairs, deceiving the brain into producing the sense of motion, or spinning. When in the dark—in other words, in bed after a drinking bout—the spinning sense is enhanced, since you can no longer rely upon visual cues to counteract the false sense of motion.

Luckily, as the night wears on, your blood alcohol levels subside and the spinning feeling gradually fades away. If you’re stuck with a spinning head, though, these moments can stretch on and on. Unfortunately, preventative measures backed by science are few and far between. Besides the radical “medicine” of simply abstaining from heavy drinking, it seems hangover symptoms can be lessened by drinking beverages containing more pure ethanol such as gin and vodka rather than things like whiskey and red wine, which contain more add-ons. So next time you’re out drinking, go for the vodka-cranberry instead of the whiskey sour and save yourself some of the headache. Either way, though, if you overindulge, you’re probably in for a tilt-a-whirl-like ride.