What are Essential Oils?

Aren’t essential oils just nice smelly things?

No. Plants produce essential oils to protect themselves against environmental threats and are a critical part of a plant’s immune system. Nature ensures that the majority of essential oils are found in the part of the plants that are the most vulnerable, with the greatest risk of attack from microorganisms – flowers, seeds, roots, leaves, bark, and stems.

Who liked science at school?

If like me you were not interested in science at school, then the thought of this article may be concerning! In the past few years since I have discovered essential oils, I am fascinated by the science of what they are, how they work and why they help us!  I was never taught science like this at school!

Seriously, science?

But what exactly are they?  Essential oils are aromatic extracts composed only of volatile molecules from the plant.

With me so far? I wasn’t at this point so don’t worry!

Volatile – They are small molecules that can change their state – liquid, gas, solid depending on the surrounding environment. When we say small – we mean small. One drop of essential oil contains 40 million trillion of them.

Aromatic – They contain an aroma that can be detected by the majority of people. Not all compounds are aromatic. Think Water!

Compound – A chemical substance composed of multiple molecules made from atoms from multiple elements attached together. Mind blown yet? For me this made sense when I was told to think – Water! The most common compound of all. Made of multiple molecules of Hydrogen (element) and Water (element) – Hence we know this as H2O.

Every oil has it’s own chemical makeup – or composition. Meaning they contain different elements and in differing percentages. Some essential oils may only have 2 or 3 compounds, others have dozens of compounds and a few even have over 100 compounds.

So what in them makes them beneficial?

Now here it can get complicated – really complicated! Studying has finally made some sense to me, but no matter how hard I try and phrase it in my mind, I have not found an easy way to describe it! It has taken a long time and even now I am not confident I can truly explain it. So I’m just going to say please trust me or go and research yourself!

Jumping a few steps of science ahead…

The chemical makeup of essential oils can be subcategorised into ‘functional groups’ . Alcohols, aldehydes, alkenes, ketones, esters, ethers, phenols, and phenylpropenes.

It is these functional groups that contain the properties, therefore the best uses and ultimately the benefits of each essential oil. This is why an essential oil can have so many benefits. If it contains compounds from multiple functional groups, then the essential oil will provide the therapeutic benefit associated with the specific functional group.

So what am I looking for?

In summary, essential oils are by the sheer nature of their make-up and variety, complex matters.

Where to start, how to use them and making sure you have the best is a challenging journey that is neither simple nor clear. Essential oils are so readily available these days, but this does not make them safe, nor everyone knowledgeable. 

Whether it is myself or any professional aromatherapist, my simple advice – work with someone that understands the science. If you truly want to get the full benefits of essential oils, rely on the best oils and the knowledgeable people. 

My plan? To ensure that the education continues.

But for now a little more science to give you an insight to what oils may help, when and what to start considering. 


Relaxing aromas and help to soothe anxious feelings. Repellant and cleansing properties and supports healthy skin. Supports the circulatory system, calms the nervous system.

Example oils – Tea Tree, Geranium, Coriander, Basil, and Lavender.


Calming, relaxing and protecting. Provide a warming sensation to the skin and support a healthy oral care protocol. Supports the health of the cardiovascular, digestive, immune, and nervous systems. Many essential oils high in aldehydes are also known to support a healthy metabolism.

Example oils – Cassia, Cinnamon, Melissa, Lemongrass, and Lime.


There are 2 different types of alkenes but both contain antioxidant properties for both the skin and tissues. May also support the nervous, immune, digestive, reproductive, integumentary, and circulatory systems.

Example oils – Frankincense, Douglas Fir, Blue Tansy, Lemon, Wild Orange, Ylang Ylang, Black Pepper, Copaiba, Melissa, and Ginger


Relaxing, soothing and balancing. Considered supportive and protective against certain kinds of environmental threats. Some esters can support the health of the cardiovascular, immune, nervous, and digestive systems.

Example oils – Lavender, Roman Chamomile, Helichrysum, Arborvitae, and Wintergreen


Another group where are 2 different types. Both are soothing to emotions and promote feelings of clear airways. Additionally, considered to contain surface-cleaning properties. Provide antioxidant support and can also support proper immune system function.

Example oils – Cardamom, Eucalyptus, Rosemary, Melaleuca, Peppermint, Myrrh and Vetiver.


Some are energising and uplifting, others are stabilising and grounding. Support digestive, gastrointestinal, and nervous system function and health.

Example oils – Spearmint, Dill, Peppermint, Geranium, Caraway, Spikenard, and Frankincense.


Invigorating aromas, with powerful cleansing properties for the skin and surfaces. Also, they also provide antioxidant properties and support the proper function of the cardiovascular, circulatory, digestive, gastrointestinal, immune, nervous, and respiratory systems.

Example oils – Thyme, Oregano, Clove, Cinnamon Bark, and Basil.


Energising aromas offering support to overall skin health and appearance. May support the cardiovascular system and promote healthy blood flow.

Example oils – Fennel, Myrtle, Anise, Star Anise, and Basil.

Annika Vincent Essentially Serene Clinical Aromatherapist