Essential oils have changed my life. I use them as medicine and I’ve developed a toxin-free skincare line based on them. They are liquid miracle workers, as I like to call them, that are brilliantly complicated and extremely powerful. Let’s see what these little powerhouses are made of!
Essential Oil Chemical Constituents
Essential oils are unique and multi-dimensional possessing hundreds of chemical constituents. Each chemical constituent is responsible for the oil’s taste, smell, and medicinal properties. There are two very distinct groups of chemical constituents; hydrocarbons, which are made up of almost all terpenes (monoterpenes, sesquiterpenes, and diterpenes), and oxygenated compounds, which are made up primarily of esters, aldehydes, ketones, alcohols, phenols, and oxides (Higley, 2009).
Monoterpenes, sesquiterpenes, and diterpenes make up the terpene chemical group. Chemists differentiate the various groups of terpenes by the number of carbon atoms they contain. Monoterpenes have ten carbon atoms, sesquiterpenes have fifteen, and diterpenes have twenty (Keville, 2009). Monoterpenes are in most essential oils and are capable of performing many different functions. “Most tend to inhibit the accumulation of toxins and help to discharge existing toxins from the liver and kidneys,” (Higley, 2010). Monoterpenes have a stimulating effect and can sometimes irritate the skin. If you’re going to apply oils containing monoterpenes topically, be sure to use an organic carrier oil to dilute the essential oil. This way you will lessen the chance of skin irritation. The following is a list of the most common monoterpenes: a-pinene, b-pinene, camphene, b-myrcene, and d-limonene. Most citrus oils consist of monoterpenes, as well as pine oils, black pepper, and nutmeg.
“Esters are the compounds resulting from the reaction of an alcohol with an acid,” (Higley, 2010). Esters can be found in many oils, especially in mild ones, and are considered to be the most balancing out of all the chemical families of essential oils (Keville, 2009). Essential oils that contain esters are calming, antifungal, and antispasmodic. Common chemical constituents having esters are linalyl acetate, geranyl acetate, eugenyl acetate, neryl acetate, bornyl acetate, and lavendulyl acetate. Lavender and clary sage both contain esters.
Aldehydes are responsible for giving essential oils their smell. Oils containing aldehydes are mostly sedating and give off very strong aromas. These oils are usually anti-inflammatory, anti-infectious, fever-reducing, hypotensive, calming to the central nervous system, and tonic (Higley, 2010). Citronella, melissa, lemongrass, lemon myrtle, lemon verbena, cinnamon bark, and lemon eucalyptus all contain aldehydes. A lot of these oils can cause skin irritation when applied topically. If you are applying these essential oils topically, be sure to use a carrier oil such as almond, olive, jojoba, or castor.
“Ketones stimulate cell regeneration, promote the formation of tissue, and liquefy mucous,” (Higley, 2010). Other actions of ketones are cicatrizant (heal wounds) and lipolytic (dissolve fats). Some ketones when isolated from other constituents are mucolytic and neuro-toxic. There haven’t been any documented cases of toxicity on a human from using essential oils containing ketones. Someone would have to consume A LOT of oil with ketones in it to be affected in a negative way. Sage, hyssop, rosemary, mugwort, tansy, and wormwood all contain ketones. Many aromatherapists have different views on the use of ketones and which ones they think will have a toxic effect. Keville says, “Potentially toxic ketones are found in sage, hyssop, pennyroyal, and thuja, none of which we recommend using. Their toxic effects vary depending on the plant, but irresponsible use of oils in this group can have abortive, convulsive, stupefying, or epileptic actions.” It’s best to do as much research as possible, consult a registered aromatherapist, or simply use an alternative essential oil.
Essential oils that have alcohol chemical constituents are known for their antibacterial, anti-infectious, and antiviral properties. They are generally non-toxic, stimulating, and can increase blood circulation. Linalool, citronellol, geraniol, and farnesol are all monoterpene alcohols or monoterpenols. Sesquiterpene alcohols or sesquiterpenols are antiallergenic, antibacterial, anti-inflammatory, and a liver and glandular stimulant. Bisabolol is one of the strongest sesquiterpene alcohols according to the Reference Guide to Essential Oils. Oils that have alcohols constituents are palmarosa, peppermint, and coriander.
“Phenols are the most powerful antibacterial, anti-infectious, and antiseptic constituents in the plant world,” (Higley, 2010). Oils that are high in phenols have high levels of oxygenating molecules and have antioxidant properties. You must proceed with caution when using oils high in phenols. They can be extremely caustic to the skin and can be toxic to the liver. You must dilute these oils in an organic vegetable oil such as olive or almond to minimize any negative effects on the skin. Eugenol, thymol, and carvacrol are all phenol containing chemical constituents. Essential oils that have phenols are oregano, thyme, and tea tree, peppermint, thyme, and wintergreen.
Oxides are known to be mildly stimulating and expectorants. Some commonly known oxides are 1,8-cineol or eucalyptol, linalool oxide, ascaridol, bisabololoxide, and bisabolone oxide. Oxides can be found in cardamom, German chamomile, eucalyptus globulus, eucalyptus polybractea, cajeput, niaouli, myrtle, ravensara, and rosemary (CT cineol) (Higley, 2010).
Why is this information important?
Having a basic understanding of how an essential oil works is important. When formulating blends for people with certain skin types, or taking essential oils internally, you will need to know if there’s potential for a bad reaction. Essential oils are really powerful and knowing a little bit about the chemistry of these oils makes preparing medicines and skincare formulations a lot easier and safer.
Higley, C. & A. (2010).Quick Reference Guide for Using Essential Oils. Twelfth Edition. Abundant Health: Spanish Fork, Utah.
Keville, K. (2009). Aromatherapy. Crossing Press. Berkeley, CA.