Way before there were multilevel marketing companies selling essential oils by the pound, there were wise healers accessing the benefits of essential oils by making poultices, salves, and medicinal teas from the raw plants. In fact, plant medicine was the only medicine for thousands of years until the pharmaceutical industry began to provide other options. Now, as the pendulum swings from the prescription pad back toward the power of plants, it’s a great time to make sure you understand what essential oils are, how they’re made, and how to use them safely and effectively.
What is an essential oil?
An essential oil is the extraction of a plant’s aromatic essence—the "quintessential" oil of the plant. Each plant has its own reason for making these essences. In some, the oil attracts pollinators or repels predators. In others, the oil discourages nearby competitive species from growing too close. An essential oil can even serve as a built-in antimicrobial system, keeping the plant protected and pest-free.
Essential oils are created by glandular structures in the plant, either on the surface or internally. If you touch a lavender leaf, for example, you can smell the essential oil on your fingertips from the external oil glands. With a plant like eucalyptus, you have to break open the leaf to access the aromatic compounds. In either case, when it comes to incorporating essential oils into wellness, it’s often more practical—and accessible—to work with a concentrated essential oil than the raw plant itself.
How are essential oils made?
There are two main ways to collect a plant’s essential oil: distillation, the oldest and most common method; and expression, most commonly used with citrus oils. A newer method called CO2 extraction is gaining popularity but is still not considered mainstream by most aromatherapists. Concretes and absolutes, often used in natural perfumery, require solvent extraction and are not considered "pure," though they are invaluable to the natural perfumer. All methods require a deep understanding of how and when to harvest plant material for maximal yield of the best and most powerful aromatics.
1. Steam distillation.
The most common method of producing essential oils is steam distillation. With this technique, steam is passed through a large hopper (like a steamer basket in your kitchen) containing raw plant material, causing the plants to release their aromatic compounds, which vaporize and rise with water vapor (steam) into a closed cooling system above the steaming chamber. As the combined steam and plant vapor is cooled in another chamber called a condenser, the vapor turns back into liquid. From here, they travel to a separator, where they split into water on the bottom and oil on the top. The water contains the water-soluble (hydrophilic) parts of the plant’s essence, which is why the remaining water is called a floral water, or a hydrosol. The oil-soluble aromatic compounds rise to the top of the hydrosol in a separate layer, which can be decanted off: This is the essential oil of the plant.
This same procedure is used in hydro-distillation, where the plant material is actually submerged in water, and in hydro-diffusion, where steam is forced in from the top rather than passed through the plants from the bottom. Not all botanicals can withstand this high-heat method of extraction, which is why other methods exist.
Citrus oils are obtained by expression (also known as cold-pressing or expeller-pressing, the former being a temperature-controlled process). The peels are first pricked all over to puncture the cells containing the oils, and/or soaked in warm water, and then mechanically pressed. The pressed liquid and pulp are then centrifuged, where they separate into citrus juice and essential oil. Citrus peels are often obtained in bulk as a by-product of the citrus juice industry, which is why many of these essential oils (lemon, orange) are readily available and inexpensive. Contamination with pesticides is a real concern in the collection of citrus essential oils, so it’s a great place to invest in certified organic oils.
3. Solvent extraction.
The rest of the aromatics, not technically considered essential oils, are obtained using solvents: hexane, dimethyl ether, or supercritical carbon dioxide. With hexane and ether, the residue is typically less than 10 ppm (parts per million), which is fairly negligible. The least toxic of these solvents, though, is carbon dioxide (CO2)—as in, the stuff you just exhaled.
In this method, which is gaining popularity, the solvent, CO2, is placed in a chamber with the plant material. The chamber is then put under extreme pressure (100 to 200 times normal atmospheric pressure), at approximately 85 degrees Fahrenheit. This combination of mildly increased temperature and hugely increased pressure puts the CO2 into a "supercritical" state. This is a nerdy concept, but it’s where the CO2 is part liquid and part gas (like a dense fog), which allows aromatic components of the plant to dissolve in the CO2 fog. The supercritical CO2, now containing extracted aromatic compounds, is separated from the remaining raw plant material, and then returned to normal atmospheric pressure, where carbon dioxide can only exist as a gas. When it changes back to gas, it leaves behind ONLY the extracted aromatic part of the plant. There is literally zero residue of the solvent in the remaining CO2 extract because the solvent has changed physically from a supercritical state to a pure gas. It’s a very cool trick, and a very expensive one, so its utility is still fairly limited.
Long ago, people used a technique called enfleurage to capture the essence of delicate flowers like jasmine and orange blossom—flowers were combined with animal fat and pressed between pieces of glass. After a few days, the flowers were removed and replaced with fresh flowers—this process was repeated for several rounds until the fat was as full of the desired aroma as possible. This technique is used much less frequently now, as most people do not want their personal care products to be animal-derived. In most instances, concretes and absolutes have taken the place of enfleurage.
Essential oils: concretes and absolutes.
A concrete is made by combining plant materials, a solvent (hexane or ether), and waxes or resins. Once combined, the solvent is removed by gentle heating in a vacuum (negative pressure environment). The remaining waxy compound is the concrete, which can be used to create alcohol-based perfumes. From there, a concrete gets washed with ethyl alcohol, which pulls the lighter aromatics from the concrete. The ethyl alcohol mixture is then distilled again, which removes almost all of the alcohol (>95 percent), leaving behind the extracted aromatic compounds in the form of an absolute. Natural perfumers frequently use absolutes to weave in botanicals like tobacco, oakmoss, jasmine, and rose.
How to use essential oils.
Essential oils have been used for centuries in aromatherapy, perfumery, medicine, and skin care. There are a lot of recent health claims out there about essential oils, especially as they become more available in the mainstream marketplace. While there’s still much research to be done on the healing potential of essential oils, it’s clear that they are powerful, and need to be used with caution. Here are a few easy, effective ways to use essential oils in your daily life:
1. Inhalation and diffusion.
Inhalation is one of the easiest ways to use essential oils in your home. You can use a diffuser, sprinkle oils on the shower floor as you bathe, or drop them into a tissue and inhale them. There’s mounting evidence to show that certain inhaled essential oils can help with conditions like migraines and anxiety.
2. Topical application.
Most essential oils are too acidic to be applied undiluted, directly to the skin, with a few exceptions. One exception is lavender essential oil. There is evidence to support the use of lavender essential oil as an analgesic (pain reliever), anti-inflammatory, and topical antibiotic, making it very handy to keep around for burns and bug bites.
Essential oils can also be applied to the skin in the form of skin care products. Of course, not all oils are appropriate for skin care, and the concentration is important, so make sure you’re buying from a company with an educated formulator.
3. Household cleaning products.
Some essential oils, like lavender, cinnamon, geranium, and thyme, have powerful antibacterial properties, making them excellent choices for DIY home cleaning products. Plus, you’ll reap the emotional benefits of inhaling these beautiful scents!
Want to start using essential oils? Here are the best ones for combatting stress and anxiety.