Demystifying chemotypes: get the most out of your essential oil blends

Apr 12, 2023

If you’ve used essential oils, you most likely have come across the term chemotypes. But do you really know what they are, and why it is important information to know? Let’s dive into the topic of essential oil chemotypes.

What are chemotypes?

Chemotype (noun): Essential oils that are from the same plant species, but whose dominant constituents differ in their chemical composition.

To put it as simply as possible, essential oil chemotypes are plants of the same genus and species that are identical in appearance but have distinct internal differences. This means that, despite coming from the same species of plant, various chemotypes of essential oils can be produced. The resulting essential oils have different therapeutic and safety considerations when used in aromatherapy. The aroma of the chemotypes are also different due to the variance in the chemistry of the essential oil properties.

A quick analogy can help explain chemotypes further. If a woman gives birth to identical twins and gives them up to two different families for adoption, the twins will have similarities because of their genetics, but they will also have significant differences because of the environment they grew up in.

Common essential oil chemotypes

The most common example of this is rosemary essential oil. It has several chemotypes: rosemary CT1 (Salvia rosmarinus CT camphor), rosemary CT2 (Salvia rosmarinus CT 1,8-cineole), and rosemary CT3 (Salvia rosmarinus CT verbenone).

Rosemary CT1 contains more of a constituent called camphor, and would therefore be more suitable for muscular aches and pains.

Rosemary CT2 contains more 1,8-cineole, making it a better choice for respiratory conditions. Rosemary CT3 contains more verbenone, and as a result it would be better for skin conditions.

What this means: If your bottle of rosemary essential oil is only listed as rosemary (Salvia rosmarinus, formerly Rosmarinus officinalis), you are unable to determine the further chemistry of the oil.

Why does the chemotype of an essential oil matter?

It is important to know the chemotype of the oil you are using so that you can ensure it is the right one for your purpose. A large number of essential oil suppliers do not list the chemotype as it is generally inferred that the contents of the bottle are rosemary CT1. This type of rosemary is the most often traded oil on the market. The aroma will be a giveaway as to the chemotype too, as generally the CT1 variety has a more eucalyptus-type smell. Regardless, the chemotype (CT) should be noted; when in doubt, ask your preferred supplier for further information.

The therapeutic properties of an essential oil can be determined by chemotypes, which is why they are significant. For example, two oils from the same plant may have various chemotypes and impact the body in various ways. It is possible that one oil is calming and the other is uplifting. The safety of the oils varies as well.

Importantly, the dermal limits and safety considerations for each chemotype vary. Rosemary camphor CT has a dermal limit of 16.5%; while rosemary verbenone CT has a 6.5% dermal maximum (Tisserand & Young, 2014).

Holmes (2016) notes that although the chemotypes make the oils different, we should not think of them as different essential oils. He states that “each chemotype contains all three constituents (cineole, camphor, and verbenone) but in different proportions.”

How to determine the chemotype of your essential oil

If your preferred essential oil supplier doesn’t list the chemotype on the bottle, you may need to look at their website and other supporting documentation. Look at what they list as the main chemical constituent. While this may not be a precise indicator, it may give you some insight. Contacting the supplier directly for the precise chemotype is also a good idea.

More examples of essential oil chemotypes

Besides rosemary, the most common essential oil chemotypes in aromatherapy are:

  • Thyme
    • Thymus vulgaris CT thymol
    • Thymus vulgaris CT linalool
    • Thymus vulgaris CT carvacrol
    • Thymus vulgaris CT geraniol
  • Basil
    • Ocimum basilicum CT linalool
    • Ocimum basilicum CT carvacrol
    • Ocimum basilicum CT eugenol

There are a number of other examples of chemotypes, which we cover in our Professional Level Certification Program in more detail so that you know how to use them safely and effectively in your therapeutic blending. Explore the curriculum for this innovative, in-depth aromatherapy certification program.

Why are there different essential oil chemotypes?

It is believed that different growing conditions, soil conditions, and environmental factors all play a part in the plant producing chemical differences.

Sustainability and essential oil chemotypes

Commonly used chemotypes may not always grow well in certain regions, and therefore there are new chemotypes emerging as a result of impacts of climate change. It is important to take into account that if we want to preserve ecosystems and plant resiliency in the face of climate change, then we should not limit ourselves to common chemotypes. This also highlights why it is important to know and understand essential oil chemistry and how we can use that knowledge to choose oil alternatives.

In closing

Before purchasing your next bottle of rosemary, thyme, or basil, make sure you look for the chemotype information to ensure you are purchasing the one that you need for your needs. It really will make a significant difference to your aromatherapy practice and preparations.

Questions? Let us know in the comments!

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.


Essence of Thyme College of Holistic Studies (n.d.). Module 1: Lesson 4 [Course lesson] In Professional Aromatherapy Certification Program. Essence of Thyme College of Holistic Studies. 

Holmes, P. (2016). Aromatica: A clinical guide to essential oil therapeutics. Volume 1: Principles and profiles. Singing Dragon.

Tisserand, R., & Young, R. (2014). Essential oil safety: a guide for health care professionals (2nd ed.). Churchill Livingstone.


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