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An Insight into Essential Oil Composition

On average, an essential oil can have from 20-200 organic compounds within them, most at percentages of less than 1%. Depending on the potency of the compound, even at these levels it could add additional therapeutic actions to the overall oil composition.

Notes and Evaportion

Essential oils are volatile, meaning they evaporate, slowly over time. There are different levels or what is known as notes of evaporation rates or times; top, top-middle, middle, middle-base and base, being the slowest evaporation rate of oils. Think about that the next time you are smelling a blend and how the aroma changes over time. It happens slowly so we don’t immediately notice the subtle changes but over time you’ll notice the slight change. It’s a beautiful trait of essential oils.


We always say essential oils and water do not mix. They have a small degree of solubility to water but not significant enough to being anywhere safe to ingest.

Essential oils are lipid-soluble substances meaning they can enter a cell by dissolving in the lipid portion of the membrane (enter in through our skin) and diffuse through it. The greater the lipid solubility, the more readily a molecule (essential oils are tiny molecules) will pass through the membrane. By diluting in a carrier substance it “fixes” the essential oils, allowing more of the essential oil to penetrate through the skin. This is accomplished by the essential oil binding to the carrier oil and this in turn slows the evaporation rate, allowing more to penetrate through the dermis (skin) before completely evaporating and at the same time protecting the skin. Many oils will cause an allergic type reaction, whereas the carrier oil, when used in accordance to proper dilution rate(s) per oil, will protect the skin.

Distillation and more

Essential oils are obtained through a few different methods, cold-pressed (citrus oils) or distilled. A few other methods of extraction includes CO2 extracts, absolutes, resinoids and concretes.

To explain, during the distillation process, after the solvent has been removed there is a near solid wax-like substance and that is called a 'concrete'. Had resinous botanical material been used to extract, the result would be called a 'resinoid' instead of a 'concrete'.

There can be variations in the concentration or percentages of constituents in essential oils. This is due to the environment where the plant grows. It can be from the climate and growing conditions, the harvesting time, genetics and the distillation process. My former instructor explained she had gotten the same oil from the same distiller for a long time but then received a new batch and it tested completely different. In calling the distiller, he said there had been much more rain than usual and a mud slide. It’s amazing how it changed the composition of the oil. It stands to reason that requiring a GC/MS report from a company for each new batch of essential oil is not only reasonable but necessary, especially if you component blend.


Some plants can have chemotypes (ct.). If one applies, knowing the chemo type is important in essential oils. A chemotype (sometimes chemovar) is a chemically distinct entity in a plant or microorganism, with differences in the composition of the secondary metabolites. Minor genetic and epigenetic changes with little or no effect on morphology or anatomy may produce large changes in the chemical phenotype.

Why does this matter in essential oils? A good example is Thyme ct. linalool and Thyme ct. thymol. The linalool chemotype is gentle and can be used safely, even with children. The Thyme ct. thymol is quite the opposite and is very irritating to the skin and can irritate the mucous membranes. It also has some potential drug interactions to be concerned about.

Wating for Adulteration

Essential oils are often subject to adulteration. We do everything we can to avoid this happening. One of the worst things to do is take the word of a salesperson or company. There are some assurances in place. Use head organizations in Aromatherapy to guide you in choosing a reliable company such as the National Association of Aromatherapy (NAHA) and Alliance of Holistic Aromatherapist (AIA). Using these sites gives you websites, listings of schools, books, Aromatherapists from various degrees of learning, blogs and so much more.

When going through the sites, look for ones that offer not only the therapeutic actions of the oils but botanical names, the chemotype as discussed above, safety on oils, shelf life of oils and a GC/MS report for each batch of oil. Keep your GC/MS reports. I keep mine in a binder. Also look at other reports from other companies; I keep these in a binder as well. When purchasing a new oil, I look at the report before buying the oil. If I see a questionable variance in the report compared to the other reports, it sends up a red flag. This helps to avoid adulterated oils. Nothing is fail proof but this helps tremendously. If oils are adulterated, it can increase the toxicity rate of an oil and as such not safe to use.

The best way to preserve your oils is by keeping them in their dark brown bottles in a cool, dark dry place. A good temperature can be around 60-65 and a mini-fridge seems to works quite well for these purposes. Oils have shelf lives and by storing them properly, you get the full shelf life from them. As soon as you open your bottles the first time, mark the date on them as this starts their shelf life. Some oils, such as citrus oils, are especially sensitive to light and air.

Helpful Related References:

1. By Robert Tisserand|2016-01-19T23:06:54 00:00August 9th, 2015|Interview, Safety|2 Comments. (n.d.). Robert Tisserand interviewed on ingestion, dilution and other safety issues. Retrieved December 25, 2015, from

2. Learning About EOs – Using Essential Oils Safely. (n.d.). Retrieved February 2, 2016, from

3. Tisserand, R., & Young, R. (n.d.). Essential oil safety: A guide for health care professionals (2nd ed.).; dermal and inhalation dosing; pgs. 48-50

4. Tisserand, R., & Young, R. (n.d.). Essential oil safety: A guide for health care professionals; Oral and Inhalation Dosing; pg. 40-50

5. Tisserand, R. (n.d.). Essential Oil Safety: Second edition (2nd ed.); Inhalation; pg. 658

"Just a Drop of Thought for the Day" Rehne

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