When buying an essential oil you may see the abbreviation “ct.” as part of the plant name (e.g. Thyme ct. Linalool). The designation ct. is short for chemotype, and it identifies a plant that has a chemical distinction. Most essential oils do not have various chemotypes, but in cases where an essential does it is to indicate a difference among essential oils from the same plant species.
Dr. Robert Pappas of Essential Oil University states that “an Essential Oil Chemotype refers to variability in chemistry that can occur in oils coming from the same genus and species. The primary factor for the difference in chemistry in most chemotypes is due to genetic variability within the plant species of interest. Other factors can include geographic location, climate, altitude, insect interactions and other environmental aspects. Many times the chemotype will refer to the main component of the oil, such as in Basil ct. Linalool or Basil ct. Methyl chavicol. But it’s important to note that the chemotype listed may not always be the main component of the oil, for example in Rosemary ct. Verbenone, the verbenone is never the main component (1,8-cineole is still primary), it’s just a drastically elevated level of verbenone.”
This chemotype identification becomes part of the consideration in choosing the proper oil to use. Different chemotypes can have different therapeutic properties. Although the chemotype chemical listed may not be the major constituent of the oil, it can drastically change the instances in which the oil is used. It can also change the scent profile. I mentioned Thyme ct. Linalool above because that is the type of Thyme essential oil that I prefer – it is sweeter and gentler making it easier to incorporate in blends for a broader range of people.
So, when using Aromatherapy to address a specific concern, analyze plant chemotypes when they are available. It can give you a larger scope of essential oils to choose from, even within species of the same plant.