What can essential oils do for you? Use “sweet orange to quell anxiety,” “lavender to sleep better,” and “rosemary for better focus at work,” says health.com. Essential oils are made by cold-pressing or steam-distilling plant material. They’re usually inhaled as part of “aromatherapy,” though some people recommend swallowing or rubbing them on your skin. Some studies report subtle effects on anxiety, stress, or thinking ability, but “the quality of the trials is often deplorably low,” says Edzard Ernst, emeritus professor of complementary medicine at the University of Exeter in Britain. So why do some people swear by essential oils? It may be the power of suggestion.