It sounds ludicrous, really — who believes that something as unimportant as the color of their drink would cause their hangover? But actually, this is the most important factor in alcohol-induced hangovers (besides drinking too much ethanol in the first place). During the process of making alcohols, chemical by-products called "congeners" are created by the fermentation and distillation procedure. These congeners are a chemical mixture of impurities and often give dark beers and liquors their color. They also are sometimes purposefully added to alcohol to create certain flavors. High-congener beverages are known to cause worse hangover symptoms when compared to drinks with less of them. While present in light alcohols — like white rum, gin and vodka — congeners can be found in much larger quantities in dark alcohols, such as whiskey or stout beers. Additionally, you are much more likely to find congeners in lower-quality liquors than in higher-quality spirits, which have typically been distilled more times to reduce the amount of impurities. So next time you're ordering a drink, ask the bartender to reach for the top-shelf instead of the well liquor, and opt for light over dark rum.