I was reading a Facebook post recently where essential oils were being discussed, particularly cassia vs. cinnamon bark oil. There was a debate over whether two plants from the same genus were essentially equals. Should we refer to both peppermint and spearmint as mints (mentha)? Should we refer to both cassia and cinnamon bark as cinnamon? The answer provided by the chemist leading that particular page was NO, just because they are from the same genus does not make them equal and knowing this is important, not just in aromatherapy but in herbalism also and here are a few good reasons why.
When I studied herbalism and aromatherapy there was a lot of emphasis on learning the latin binomial of each plant. In fact, latin names were the first on the list to memorize, they repeatedly appeared on exams and quickly it became very apparent why.
Example: lavender essential oil is made from several varieties of the species Lavandula. Each species contains various chemical constituents and none are exactly the same. Using the oil from one species can have a different effect on you than if you use one from another species.
Lavandula intermedia - known for its ability to stimulate
Lavendula augustifolia - known for its ability to help people relax
Another example is cinnamon essential oil vs. cassia. If go to the store looking for cinnamon essential oil you'll see cinnamon eo labelled two ways but both have the same scientific name; Cinnamomum zeylanicum. The bottle will be labelled either "cinnamon bark" or "cinnamon leaf" and the latin name will be listed as well. (at least this is how reputable companies label)
Cassia oil is known as a Chinese cinnamon oil but it is always labelled as Cassia on a bottle of essential oils unless someone is trying to mislead the consumer. A bottle of cassia should also contain the latin name Cinnamomum cassia.
There is no confusing the two essential oils if labelled properly. Problem is, many companies will label an essential oil as C. zeylanicum when it's actually C. cassia and in the world of spices the same occurs. A company could pay the price for C. zeylanicum which is costly but receive C. Cassia which is much cheaper. Ingesting C. cassia as a medicinal or even just as a food item is also an issue. If you want to understand why read this, Tis the Season for Cinnamon or this Cinnamon's Dirty Little Secret Revealed. In short, it has to do with the coumarin and cinnamaldehyde content.
When an herbalist reaches for C. zeylanicum (synonym Cinnamomum verum) they are interested in the chemical constituents found in C. zeylanicum, not C. cassia.
I hope I explained that well, let me know if it doesn't make sense.
Why someone with no scientific background would find it appropriate to argue about this with a chemist that makes a living analyzing essential oils is beyond me but I'm grateful to whomever that woman was because it brings up an important issue about the use of essential oils that I don't think gets addressed often; individuals selling and promoting a product they know nothing about. It also made me reflect on my own lack of understanding of how herbs and essential oils worked in the years prior to getting certified in both - like in college when I dumped an entire bottle of peppermint essential oil into my bathtub not realizing that eos and water don't mix. I'll just say… the results of that mistake weren't pretty.