If you're a beer connoisseur, you may know hops as the ingredient that gives certain brews their bitter punch. In addition to affecting taste, those bitter hops act as a preservative in beer because they fight nasty beer stink. They do this by stopping the growth of bacteria, and thus, the spread of odor in beer; it turns out they can do the same for your underarms. When applied as a deodorant, hops extract serves as an antimicrobial agent, so that bacteria in the armpits don't get a chance to interact with sweat. Tom's of Maine uses hops in many of their natural deodorants.