Drink dark liquor and get a hangover, drink light and you are good all night. Congeners are in alcoholic beverages, mostly as a result of the processes used in fermenting and aging, or are leached from oak barrels. They are toxins such as acetone, histamines, and tannins. Although they are only slightly toxic in the small amounts found in booze, some believe congeners are to blame for typical hangover symptoms. Gin and vodka have the least congeners while bourbon and scotch have the most as dark liquors have more than clear ones in general. However, the biggest determinant of getting hung-over is alcohol intoxication, not dark vs. light drinks.
The old saying: “Beer before liquor, never been sicker. Liquor
before beer, you’re in the clear.” People tend to down liquor but
sip beer. As such, drinking liquor first might do more damage
because of greater speed of drinking. The one truth in this adage
is that if you drink much beer before drinking much liquor, you
very well could get sick. The truth is that it is more about how
much you drink than the order you drink it. If you drink enough,
you will probably get sick either way.