Chemistry. Already getting nervous? The chemistry chapters of essential oil texts are the most frequently skipped, even by natural health professionals. But it can be fun and useful…really! Knowing what essential oils are made of, and how this affects their aroma and therapeutic value can have a big impact on the efficacy of your aromatherapy practice. Understanding the basics can help you make better choices in essential oils, and better choices in their application. Plus, this can give you the foundation for further understanding of true ‘medical aromatherapy’, as practiced in much of the rest of the world. So here’s a primer on the chemistry of essential oils, with some common examples and important tips to help you grow as a holistic medicine practitioner.

So what is it that makes an essential oil different than every other oil we’re familiar with? They don’t feel the same, they don’t act the same, and they certainly don’t smell the same. Essential oils and the so-called ‘fixed’ oils (you may also know them as carrier or base oils - like Sweet Almond, Apricot Kernel, Evening Primrose, etc) are distinctly different in their molecular structure. While both essential and fixed oils share common basic atomic elements of Carbon and Hydrogen, that’s really where the similarity ends. Fixed oils are made of triglyceride structures - three long chains of carbon atoms, with hydrogens bonded at various places. The length of the chains and the position and number of hydrogens define the nature of the oil; if hydrogens are bonded to every available location, the oil is ’saturated’, for example. One missing hydrogen is ‘mono-unsaturated’, more than one is ‘poly-unsaturated’. The long chains and relative consistency of the molecular structures makes fixed oils ‘oily’, and does not allow them to evaporate quickly.

Volatile oils are another matter - volatile oils do easily evaporate, due in-part to their smaller, more complex structures. Essential oils are a sub-category of volatile oils, essential oils being specifically those volatile oils that have been distilled directly from plants (rather than laboratory made, or from another otherwise ‘inorganic’ source). Essential oils still have a core structure of linked carbon and hydrogen atoms, but they come in a great variety of shapes including short chains, rings and multiple-rings hooked together. Each of these core structures will have what is known as a ‘functional group’ attached - a sort of ‘molecular sub-unit’. Despite their seeming complexity, though, essential oils are still very compatible with mammalian biology - their atomic structure allows them to penetrate into the deepest regions of our bodies, and even to the centers of our cells.

The therapeutic action of an essential oil is primarily determined by the functional groups found in the molecules that make up that oil (here, many folks might be responding with “Say what?!?”). An essential oil is actually made up of many liquid chemicals; sometimes more than one hundred distinct chemicals are found in one pure essential oil. Each of these chemicals is formed of a carbon-hydrogen structure with a functional group attached - it is the combination of the base structure AND the attached functional group that makes a single, unique molecule. And MANY of these unique molecules combine to form ONE essential oil.

As you can see, essential oils are really very complex in their chemical nature. There are nearly infinite possibilities of functional group and ring or chain combinations. And ONE essential oil alone can be made up of HUNDREDS of these different molecular arrangements. Don’t worry, though! While it sounds complex, one needn’t know all the precise chemical details to use essential oils therapeutically. When selecting between varieties of an essential oil, It IS helpful to know that any particularly oil is often composed of one or more primary molecular forms, with many minor or ‘trace’ constituents, and that ALL these molecules contribute to the oil’s aroma and therapeutic action.

The best natural, undiluted, properly distilled essential oils with all the major and minor chemical constituents will have the finest aromas AND the most potent therapeutic action. Many factors in an essential oil’s production affect the total number and relative amounts of individual chemicals found in the final product. These include where the plant was grown, soil and climate conditions, time of harvest, distillation equipment, plus the time, temperature and pressure of distillation. This can give you an idea as to why two varieties of the same oil can smell so different: The full, beautiful bouquet of a fine essential oil will contain a myriad of notes, telling you that all natural components are present and in balanced amounts.

To best understand this, we’ll examine Lavender essential oil; more than fifty individual molecules have been identified in pure lavender essential oil. The aromatherapist must remember that ALL of these chemicals found in pure and natural lavender oil work together to produce a therapeutic effect. For example, the linalool molecule is antiviral and antibacterial; the linalyl acetate is emotionally calming; other major components including cineol, limonene, pinene and others are all noted for specific biologic and aromatic activity. It is the combined, balanced, synergistic action of these chemicals that make pure, high-quality lavender such a great healer. No one chemical can be singled out and used to give the same profound results as the complete pure essential oil.

So how is this synergy reflected in Lavender’s aroma? Each of these chemicals has a unique smell; some are sweet, some are camphorous, some citrusy and some herbaceous. It is all these chemicals together, a precise amount of each, that gives each lavender variety its distinct aroma. And your nose knows this! One can tell the difference between a well-made, complex lavender oil with many notes within the aroma, and one that is flat or plain, which may be chemically imbalanced or missing some trace constituents. One can easily tell the difference, for example, between common Lavendula officinalis, and the finer Lavendula angustifolia, which contains a higher proportion of sweet-smelling linalyl acetate and less sharp-smelling camphor. Further, lower quality lavender plants may occasionally be sprayed with linalool before harvest to enhance the production of linalyl acetate by the flowers. While the end-product may smell sweeter, the process actually creates an imbalance in the overall healing synergy of the primary and trace molecules. All these oils will be labeled ‘Lavender’ on the store shelf, yet the finer, natural lavender will have a more beautiful, balanced aromatic bouquet, and is considered the most holistically healing variety by the world’s leading aromatherapy practitioners.

All essential oils are subject to similar variations in production methods or the manipulation of their molecular make-ups through the addition of synthetic chemicals. For the most therapeutic benefit, it is always best to use true, carefully-made essential oils. To do this, find a source that is dedicated to supplying only the highest grades of oils. Examine their product’s aromatic quality and business practices and so that you are comfortable with their dedication to your health, not just their bottom line. Listen to your intuition and your own nose; they won’t lie to you! With experience, your ability to discern between subtly different grades of oils will become more astute. With even more education and skill, you’ll start to recognize individual chemicals within an oils aroma, and make the best decisions as to which oils will have the most profound therapeutic affects for you, your family, or in your professional practice.