A scientist friend tells me that when you drink beer, wine or spirits, the alcohol is absorbed in the small intestine, taken into the bloodstream to the liver where it is metabolised into two enzymes; alcohol dehydrogenase and aldehide dehydrogenase.
The first of these converts the drink into a highly poisonous volatile compound called acetyldehyde.
The body does its best to excrete this poison in the urine and on the breath, but as you can drink it faster than the liver can process it, it ends up doing all sorts of crazy things to your brain.
At first delusions appear, like how great I am, but as time goes by the brain is further affected, leading to wobbly staggers and dizzy spells until you feel wretchedly sick.
This delightful effect is helped along by the nauseatingly toxic acetyldehyde.
At this point your body (correctly) assumes that you have been poisoned by something that went into your mouth, and often decides to return the contents of your stomach to the outside world.

Waking up next morning with a tongue like sandpaper, a head that has been used for the ball in a rugby match, zooming vertigo, queeziness, and the urgent desire to be unconscious once more, you ask yourself the question – Why did I do this to myself?
Graham H Clarke, Tauranga.