Fusel alcohol

Fusel alcohols, also sometimes called fusel oils in Europe, are a mixture of several alcohols (chiefly amyl alcohol) produced as a by-product of alcoholic fermentation. The word fusel is German for "bad liquor".

Whether fusel alcohol contributes or not to hangover symptoms is a matter of scientific debate. A Japanese study in 2003 concluded, "The fusel oil in whisky had no effect on the ethanol-induced emetic response" in Suncus murinus. Additionally, consumption of fusel oils with ethanol suppressed subjects' subsequent taste aversion to alcohol, which suggested subjects' hangover symptoms were lessened, according to the journal.