Another example of pishpoor deshign.
Seriously. Too much acetaldehyde produced in alcohol metabolism - any reasonable designer ought to have anticipated this hangover thing. Plus, it's slow and involuntary - alcohol metabolism should be a rapid process, and one controlled consciously by the drinker. That way, I could drink as much as I liked, and still safely drive myself home. And this whole metabolic pathway is way too inflexible - drink ethanol, and you'll likely be okay. Drink a different alcohol - say, ethylene glycol - and you're in real trouble from the metabolites that are produced.
Yeah, this whole booze thing could be greatly improved by a competent designer, if you ask me...