Whenever you drink booze, there's an enzyme in your body that converts alcohol into a chemical called acetaldehyde. This chemical is BAD news. So another enzyme (called ALDH2) quickly gets rid of it by converting acetaldehyde into acetate (which is basically what vinegar is).
But some Asians have a deficient ALDH2 enzyme, meaning that acetaldehyde SLOWLY metabolizes into acetate. This poison basically hangs out in your blood stream for a long-ass time. This is what causes your skin to turn red, but it also causes a rapid heartbeat, fainting feeling, nausea, and other nasty symptoms like an increased risk for esophageal cancer, according to Warren.
"While the acetaldehyde makes you feel awful, it is not, technically, a hangover," said Warren.