Simplifying Essential Oil Terminology

Jan 29, 2024

Aromatherapy can be overwhelming! Educated aromatherapists use terms such as Latin binomials, chemotypes, and isomers. They discuss safety considerations; in fact, they often debate safety considerations! How can someone new to aromatherapy determine right from wrong? The easy answer would be to take an aromatherapy program, but not everyone interested in aromatherapy has the desire to be a certified aromatherapist.

Latin binomials, sometimes called binomial nomenclatures, provide a universal, consistent, and specific system for naming plants, essential for clear scientific communication and worldwide understanding. Latin binomials are very important in aromatherapy because they distinguish similar-sounding plants and essential oils from one another. If we break the word binomial down, bi means two and nomial means name, so a Latin binomial will always comprise two words or two names. The first word of a Latin binomial is always the genus, which is the generic name; the second is an individual-specific descriptive name.

Binomial names are always written in italics with the generic (genus) name first, which always starts with a capital letter. The specific (species) name always follows the generic name and will always start with a lowercase letter, e.g. Genus species.

A genus name is a “collective name” for a group of plants that all share similar characteristics. Ideally, these should all have evolved from one common ancestor. The species name allows us to distinguish between different plants within a genus. Generally, the genus and species names are Latin or Greek, but an Aboriginal name or an acronym may occasionally be used.

You are likely familiar with lavender essential oil, but did you know there are four types frequently used in aromatherapy? Each plant falls under the same genus, Lavandula, but are a different species. The most researched and used lavender essential oil is true lavender (Lavandula angustifolia). Others are lavandin (Lavandula x intermedia), spike lavender (Lavandula latifolia), and Spanish lavender (Lavandula stoechas).

True lavender (L. angustifolia) is relatively safe to use if it is used appropriately.

Lavandin (L. x intermedia) may worsen the effects of a burn, unlike L. angustifolia, which is helpful in cases of burns. Lavandin is contraindicated orally with anticoagulant medication (not that we recommend oral use in the first place!)

Spike lavender (L. latifolia) may be mildly neurotoxic based on the camphor content; the recommended maximum for dermal use is 19%.

Spanish lavender (L. stoechas) may be neurotoxic, based on its camphor content, and is contraindicated during pregnancy and breastfeeding; the recommended maximum for dermal use is 8%.

Imagine if you picked up a bottle of lavender essential oil that did not include the Latin binomial. You would not know the type of lavender, its therapeutic value, indications and, more importantly, the contraindications.

Read EOT’s blog Holy What?! Getting to the Source, to learn more about the importance of Latin binomials.

EOT’s blog Demystifying chemotypes: get the most out of your essential oil blends introduces you to chemotypes. Simply put, essential oil chemotypes are plants of the same genus and species that appear identical, but their dominant chemical constituents differ. Chemotypes have different therapeutic and safety considerations when used in aromatherapy. The aroma of the essential oil chemotypes is also different due to the variance in the chemistry. An example of a chemotype is Salvia rosmarinus CT camphor. Salvia is the genus, rosmarinus is the species, and CT stands for chemotype, which in this case is camphor. In this chemotype, camphor is the predominant chemical constituent as opposed to S. rosmarinus CT 1,8 cineole or S. rosmarinus CT verbenone. Chemotypes occur due to geographical region, climate, soil, altitude, amount of sun, and other local conditions.

Isomers are more complex, and this may be more information than you need right now! That is okay; feel free to scroll down. Isomers are all about chemistry.

Stereoisomerism is a form of isomerism where molecules have the same molecular formula and sequence of bonded atoms but differ in the three-dimensional orientations of their atoms in space. For example, the constituent linalool has stereoisomers called enantiomers because they are non-superimposable mirror images of each other: (3R)-(-)-linalool, known as licareol, and (3S)-(+)-linalool, known as coriander. The configuration at the stereocenter is designated as the left hand (S) (“sinister” or “left” in Latin) or as the right hand (R) (“rectus” or “right” in Latin).

This is essential information because isomers or enantiomers will have different properties and smell differently. For example, d-limonene, also known as (+)-limonene, is a major constituent in citrus essential oils (excluding bergamot) and has a lemony scent. D-limonene is commonly found in essential oils. Less common is l-limonene or (-)-limonene, which has a turpentine-like aroma and is found in essential oils such as dill and caraway. 

A Safety Data Sheet (SDS) is one way to inform consumers about the safety of a specific essential oil. This comprehensive document is completed either by the manufacturer or the essential oil supplier. An SDS provides information about the proper usage and potential risks of using the essential oil, including safety considerations, proper handling and how to dispose of the substance. The SDS includes the product name, manufacturer, supplier, and pertinent identification codes. It will typically provide the details and concentration of any hazardous ingredients that may impact health and environmental threats, first aid instructions, handling and storage of the product and regulatory information, such as labelling and packaging related to the product.

Some of the terms used in this post, such as hazardous, risk, neurotoxic, and contraindicated, are strong and somewhat alarming. Essential oils are natural, so they should be safe, right? Many associate the term “natural” with purity, safety, and superiority compared to synthetic substances; however, this is not always true. Hemlock and ricin from castor beans are two examples of naturally occurring substances that are toxic (poisonous). The good news is that essential oils are generally safe if you use them appropriately. Examples of appropriate use include the correct dilution based on age, condition and health of the person and the specific essential oil, application method, how often the essential oil is used (e.g., four times a day, twice daily, daily), and duration of use (e.g., days, weeks, months).

As always, we invite your feedback, questions, or comments on our blogs. You can reach us at [email protected]

About Essence of Thyme College of Holistic Studies

Essence of Thyme College of Holistic Studies offers 300- and 630-hour professional aromatherapy certification programs that help you grow a successful, fulfilling career by specializing and creating your market niche. Professional Level Certification prepares graduates to become aromatherapy consultants, launch product lines or retail businesses, or provide services as an adjunct to existing holistic health specializations. Master Level Certification and electives are ideal for certified aromatherapists seeking higher education or a path to clinical aromatherapy practice.

All Essence of Thyme programs focus on aromatherapy product development and advanced formulation, evidence-based research, spa and business management, international industry regulatory guidelines, and sustainability and conservation of essential oil and carrier oil-bearing plants.

Our comprehensive, evidence-based programs meet or exceed the criteria set forth by 5 international professional aromatherapy associations. Learn more about our aromatherapy certification programs.


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