Thyme oil has been shown to prevent the growth of bacteria associated with respiratory illnesses, among others. "Its germ-killing qualities are so effective, you'll find thyme oil as the active ingredient in many commercial green cleaning products," said Dr. Josh Axe, DNM, CNS, DC, founder of Ancient Nutrition and DrAxe.com, who noted that thyme oil is also known to be antiviral. Add it to hot water and inhale the steam.