Within a single drop of essential oil lives a complex, intricate world of relationships, bonds, and reactions that are completely hidden to the naked eye. Sometimes it can be all too easy to use our oils without giving this fact a second thought. But the precise chemistry working inside your beloved bottle of essential oil is exactly what gives that oil all your favorite qualities! So it’s worth learning about.
Not a chemistry fan? Don’t run away just yet!
As a person not particular savvy to anything more than the basic ins and outs of chemistry, I get it. The idea of looking into the microscopic happenings of essential oils can be daunting, confusing, and full of words with a few too many syllables. But whenever I’m confronted with a topic that makes my brain want to run and hide, I just remember this: learning something new is empowering! And if you love using essential oils, this information is going to help you become a more thoughtful and informed person about what it is you are using for yourself and your family. So let’s dive in!
What are terpenes, anyways?
If you love learning all about your essential oils, then there’s a term you’ve likely come across: terpene. Any single plant can contain hundreds of different compounds, which includes terpenes. Terpenes are a very large class of compounds created naturally by plants and even some insects. Essentially, these are molecules found in leaves, flowers, stems, roots, or fruit of plants that give off a distinct smell.
Terpenes aren’t around for our benefit, though. Plants aren’t working hard day and night to make sure we like how they smell, believe it or not! Terpenes actually act as a natural defense for the plant. They can ward off dangerous parasites and bugs, while also helping the plant to survive in extreme weather changes.
Terpenes are all hydrocarbons, which means that they are composed of only carbon and hydrogen elements. The carbon atoms form the framework and the hydrogen atoms attach themselves in specific ways. Their ultimate configuration leads to a specific terpene.
…and terpenoids? What are those?
You may find the words “terpenes” and “terpenoids” used alongside one another if you’ve done some personal research. They are not the same thing, but they do have a strong connection to one another. Terpenoids, also referred to as isoprenoids, are derivatives of terpenes. In an incredibly basic sense, if you took the molecular structure of a certain terpene and added oxygen atoms or other functional groups, you would have a terpenoid. Because remember, terpenes are only made up of carbon and hydrogen. Terpenoids can include other components, like oxygen, transforming them into an entirely different constituent with separate properties from their “parent” terpene .
Maybe you’ve heard of these guys…
In the essential oil world, there are two dominant groups of terpenes: monoterpenes and sesquiterpenes.
Like how both words end with “—terpenes”? Makes it pretty easy to remember!
Monoterpenes are the smallest occurring terpene molecules with only ten carbon atoms. And because they are small in size, they are also very light and evaporate quicker than other heavier terpenes. Have you heard of limonene? This constituent shows up all the time in aromatherapy! It’s in essential oils like Lemon, Pink Grapefruit, Bergamot, and Orange. Generally, limonene has a recognizable dull, citrus odor.
And here comes our constituents with those extra functional groups! Here we’ve got the incredible constituent Linalol (also spelled Linalool), found in Lavender, Basil, Ho Wood, and so many others! Menthol, the cooling constituent that gives Peppermint its signature smell and feel, is also a monoterpenol.
Sesquiterpenes are heavier than monoterpenes. They have 15 carbon atoms instead of 10, meaning they will evaporate slower. If you’re familiar with essential oil notes, you’ve probably realized that sesquiterpenes would make up many base notes, while monoterpenes make up many top notes.
Beta-caryophyllene, known for its incredibly anti-inflammatory properties, is a sesquiterpene found in oils like Copaiba Oleoresin, Black Pepper, and Ylang Ylang Complete. And Chamazulene, that unique constituent that is responsible for those incredible “blue” oils (like Blue Tansy, German Chamomile, and Blue Yarrow) is also a sesquiterpene.
These derivates of sesquiterpenes are also probably present in your essential oil collection!
So there’s a handful of well-known constituents in the large umbrella of terpenes and terpenoids. There are hundreds and hundreds of different constituents in this family, each with their own unique structure, aroma, and therapeutic properties.
So what do terpenes and terpenoids do for us?
Aside from just smelling pretty good, these compounds provide benefits to our bodies. It is within them that amazing physiological transformations can take place. According to neurologist and researcher Ethan Russo, terpenes “could produce synergy with respect to treatment of pain, inflammation, depression, anxiety, addiction, epilepsy, cancer, fungal and bacterial infections” .
For instance, we know that citrus oils are bright, cheerful, and wonderfully uplifting. Well, that is completely due to the constituents in those oils, such as limonene. We also know limonene helps stimulate the immune system by interacting with white blood cells. On the other hand, linalol has calming properties that help give essential oils like Lavender their worldwide reputation for being a go-to when you need to relax the mind and body.
Or, if you love to blend oils to make incredibly aromas, having a basic sense of terpenes may help a lot! Not only do terpenes contribute to the overall smell of an oil, but they also help determine whether that essential oil is a top, middle, or base note. Because remember, the larger the molecule is, the heavier it is and the slower it will evaporate.
This is a lot to take in.
Each terpene and terpenoid makes unique contributions to the essential oil they make up. For a single person to know the function of every constituent is a huge undertaking. However, knowing what an oil is made up of helps us make the best decisions for particular needs. Luckily we have resources to refer to when we need help uncovering the properties of a constituent, so there is no need to memorize!
And in terms of how deep we dove into this topic, we really just put our toes into the water. This is a massive topic that many intelligent people spend their whole adult lives studying. For questions or more information, please contact our team of aromatherapists at [email protected]. And don’t forget to check out our Safe Essential Oils Recipe group on Facebook to keep the conversation going!
By Katrina Scampini, Certified Aromatherapist
 Russo E. B. (2011). Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects. British journal of pharmacology, 163(7), 1344–1364. doi:10.1111/j.1476-5381.2011.01238.x
 Rhind, J. (2014). Listening to Scent: An olfactory journey with aromatic plants and their extracts. London: Singing Dragon. pgs. 129-130.