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Learning about Chemotypes

What is a chemotype?

In botany, chemotypes are kind of like identical twins. The plants look the same, but their chemistry is different, they have their own personalities.

Chemotypes happen when a plant species grows in different locations where it's affected by climate. Climate includes many things including temperature, soil, sun/shade, wind, rainfall, altitude, and terrain. For example, Jeanne Rose tells us about Rosemary, "The hotter the area the more that the Rosemary will reflect the heat by producing more camphor."

Identification You can identify a chemotype from their Latin binomial (a fancy way of uniquely classifying plants). Plants are identified by Genus then species. The Genus is always capitalized and the species in lower case and both are always in italics.

For example, Rosemary with the chemotype "verbenone" would be displayed as Rosmarinus officinalis CT verbenone. Chemotypes are not italicized but CT may also be displayed as ct in lower case.

Therapeutic differences

Speaking of Rosemary, did you know Rosemary has seven chemo types! Each chemotype of an oil has different therapeutic properties so you need to know which one is best for what concern so you get the therapeutic benefits you want. For example, Rosmarinus officinalis ct cineole is great for respiratory concerns and ct camphor works well for muscle aches, cramps and arthritis.

Other plants have chemotypes as well. The most common chemotype for Basil is Ocimum basilicum ct Linalool but Tisserand lists Basil chemotypes estragole, linalool and methyl cinnamate. Thyme oil has seven chemotypes!


Because chemotypes have different primary constituents they also have different safety concerns. For example, Rosemary ct cineole safety tells us according to Tisserand "Do not apply to or near the face of infants or children - can cause CNS and breathing problems in young children". They also carry different dilution guidelines as well. Max dermal limit for Rosemary ct verbenone is 6.5% but ct camphor is 16.5%.

I'm fascinated wondering what the plant feels that causes it to modify its chemistry based on its location and environment. Hmmm. I wonder if this also applies to us. Changing our surroundings can often change us! And sometimes a change in our perspective and attitude can make all the difference. My mom always said, "Bloom where you're planted." I think she might have been on to something.

AromaSense describes all the most common chemotypes in our Expert Notes for each aromatic (oil). Learn more at


- Rose J. 375 Essential Oils and Hydrosols. North Atlantic Books; 1999.

- Crouse L. AromaSense app. Published online 2022.

- Fulcher L. Aromatherapy Certification Program. Presented at: Aromatherapy Certification Program; 2017; Selinsgrove, PA.

- Ilić AS, Antić MP, Jelačić SC, Šolević Knudsen TM. Chemical Composition of the Essential Oils of Three Ocimum basilicum L. Cultivars from Serbia. Notulae Botanicae Horti Agrobotanici Cluj-Napoca. 2019;47(2):347-351.

- Tisserand R, Young R. Essential Oil Safety. 2nd ed. Churchill Livingstone; 2014.

- Rosemary, Chemotypes, Folklore and More. Frogworks. Accessed October 18, 2022.

- Chapman S. What is an Essential Oil Chemotype? -. Published July 11, 2016. Accessed October 18, 2022.

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