So what are essential oils?
Essential oils are also known as volatile oils because they evaporate quickly after coming in contact with oxygen. An essential oil is, simply put, the “essence” of a plant, obtained by water or steam distillation, or by cold pressing (for citrus peel oils). Through this process, the oils inside a plant can be extracted into a highly concentrated form.
“When you smell an essential oil,” says Tony Ferrari, Ph.D. in chemistry, “its constituents bind to receptor sites in the nose, which read the aroma molecules and send signals through the olfactory nerve to the limbic system and amygdala in the brain. There are more than 5,000 chemical compounds that make up commonly used oils, each of which binds in a different way to different receptors, so their effects can vary widely.”
How do essential oils work?
“Essential oils include biological compounds like growth factors, hormones, and neurotransmitters that are concentrated from the plant,” says Nada Milo, M.D. “Because different essential oils come from different plants, these components (and their resulting effectiveness) tend to change from plant to plant.”
Essential oils can have complex biochemical interactions in the human body, she says—and different essential oils can create different reactions in our enzymes and hormones. One of the active ingredients in tea tree oil, for example, is Terpinen-4-ol, which was shown in studies to kill ectoparasites found on human skin and kill infectious amoebas that cause eye infections.
One unpleasant—but totally effective—parallel you’d find in nature is poison ivy: We react to poison ivy with those awful, itchy-as-all-get-out red bumps because we’re exposed to an active compound in the plant that interacts with our skin. Elizabeth Trattner, M.D., explains that essential oils work differently—but they’re even stronger. “Essential oils can be up to 100 times more potent than the plant itself,” she says. “So their effects are visible with just a few drops.”
Basically, the active ingredients inside an essential oil can trigger “switches” inside our body. “Here’s another example,” Milo says. “An EO like lavender can stimulate olfactory nerves in the brain and cause downstream effects that slow down the central nervous system and induce a sense of calm.”