What are Congeners?
In alcoholic beverages there are impurities called congeners produced during fermentation, which are responsible for some of the taste, aroma, and color of what you drink. These impurities are not the sole cause of a hangover, yet they do seem to contribute in some manner to the severity. Not everything you drink is created equal when it comes to the concentration of these impurities. “Top Shelf” bottles generally contain fewer impurities than the type of booze you find in plastic bottles. This is because expensive liquor usually undergoes a more rigorous distillation process.
Darker colored drinks, such as whiskey, brandy, bourbon and red wine have higher concentrations than lighter drinks such as vodka, gin and white wine. In general, the fermentation and distillation processes determine the concentration in the end product. The problem with congenerics is that there are so many different types of them that not much research has been carried out to test what their exact effect is on intoxication and hangovers. However, what we do know is that for the most part our body does not like them.