Aromatherapy and the Science of Smell

Plants produce compounds that can not only affect our biology when we consume them but also when we smell them. Aromatherapy is the practice of using fragrances—usually from plants—to modulate emotions and general well-being. It’s part art and part science, but the knowledge of plants’ powerful aromas is as old as the first civilizations. The ancient Egyptians used essential oils as medicine and to prepare embalmed bodies for the afterlife. The ancient Greeks infused oils into baths and massage treatments.

Today, plant aromas can be found in some of the most common relaxation and health treatments worldwide. Studies have shown that lavender can help a person relax, and that sweet orange can reduce anxiety. In one study, women who chose to inhale jasmine, geranium rose, citrus, or lavender reported feeling reduced pain in the early stages of childbirth.

The power of these plants comes from their unique biology. After plants create their primary metabolites to process water and carbon and to photosynthesize light into sugars, they create secondary metabolites to enhance, protect, and reproduce themselves. Fragrances are among these secondary metabolites, which help a plant attract pollinators and repel predators. Plant strategies for self-preservation vary as widely as plants themselves. In the same way, a rose emits a pleasant smell to attract bees, an amorphophallus plant emits the smell of rotting flesh to lure flies and beetles that can, in turn, help it spread to other places.

Essential oils are the highly concentrated liquids of these fragrances that can be leveraged for human benefit. Their precise smell comes from the functional component (or components, oftentimes) in its key molecules, such as terpenes, esters, ketones, or alcohols. Different combinations of these components account for an essential oil-smelling floral, fruity, or something else altogether. Lavender oil, for example, includes acetate and linalool, a combination shown in pharmacological research to promote relaxation.

When they make it to human noses, smells follow a precise path to the brain. We smell with our noses, but we actually smell with a piece of tissue at the back of our nasal cavity called the epithelium. When a smell is detected, the body’s olfactory neurons in the epithelium generate a signal that is passed to the brain through the olfactory nerve. Once the signal is received in the brain, the experience is shared by the brain’s limbic system, a network that includes the amygdala (which processes emotion) and the hippocampus (which chronicles associative learning). The limbic system plays a major role in controlling a person’s mood, memory, and emotion, and it’s the reason why an offhand whiff can instantly bring you back to an event in your childhood, or remind you of your grandmother’s old perfume.

Research supports the notion that smells can quickly affect a person’s mood. In one study published in the International Journal of Comparative Psychology, half of the participants were given vials of essential oils scented with rose, vanilla, lemon, and peppermint before being asked to perform tedious tasks like word tests and anagram challenges. Those who received the fragrances reported more joy and better moods while working than the other participants who performed the tasks without fragrances. In other trials, the presence of a bad odor reduced a participant’s subjective judgment and lowered the person’s threshold for becoming frustrated.

Aromatic plant compounds are found everywhere in plants—in their flowers and leaves, of course, but also in their bark, stems, roots, and seeds. Unlike the well-known scents of roses or strawberries, some of the most powerful plant compounds are more muted and volatile, meaning they change from a solid or liquid state to a gas at room temperature. Others hide their scents in tiny hairs or in leaf glands. Using a technology known as chromatography, some scents can be detected and measured without even disturbing the plant.

But the number of scents known by humans is dwarfed by the substantial number of natural compounds still undiscovered. At Brightseed, we use our proprietary platform, Forager—which is powered by metabolomics analysis, artificial intelligence, and machine learning—to identify and map millions of undiscovered compounds that have the potential to support human health.

In our worldwide search for the most potent bioactives in nature, Brightseed is looking first into plant sources with a history of human use, such as those used in aromatherapy. Plants that have known aromatic health-promoting benefits have the potential to contain bioactives that could also influence human biology and transform human health when consumed.