I am writing this in response to a recent discussion on various facebook pages about tea tree oil (TTO), and whether a TTO with 51% terpinen-4-ol would be better than one with 41%, or whether 51% suggested adultration. Most TTO is produced in Australia and China, and this article is about the quality of Australian TTO, since the Chinese oils generally do not conform to the Australian standards, and there is no quality standard for Chinese TTO. The major constituent of TTO is terpinen-4-ol (T-4-ol). Most essential oils contain a single major constituent, and yet the main point of natural medicine is that we don’t isolate “active ingredients” and use them instead of the whole natural product.

Harvesting tea tree in Port Macquarie, courtesy of ATTIA

Harvesting tea tree in Port Macquarie, courtesy of ATTIA

Once we do that, we call it a drug. And, once we do that there is no longer any possibility for synergistic action. Synergy is the interplay, or interaction between constituents of plant-based medicines, that often give them effects that cannot be obtained by using a single, isolated substance. The action of TTO owes a great deal to its content of T-4-ol, and there may be instances when T-4-ol alone is more effective. But there are certainly situations in which the whole oil is more effective. So the question here is this: What is the ideal amount of T-4-ol, and is more always better?

There is an industry standard for TTO, and the most recent version was published in 2004. Standards for essential oils are set by the International Organization for Standardization (ISO). The actual ISO standard is copyrighted and is not in the public domain, but for the purposes of this discussion all we need to know is that the standard for T-4-ol in TTO is 30-48%. This means that any genuine, natural, unadulterated TTO should contain a minimum of 30% and a maximum of 48% T-4-ol. (For anyone who wants to better understand the way a standard can help identify if TTO is genuine there is a document on the ATTIA (Australian Tea Tree Industry Association) website: How ISO & AS Standards help identify fraudulent material.) I asked Tony Larkman, spokesperson for ATTIA, whether a TTO with more than 48% T-4-ol was a good thing or a bad thing. This is his response:

They put a ceiling on the T-4-ol to stop the bush cutters (who were distilling wild harvested material in wood fired pot stills) from cheating – it is easy to use the wrong source plant material “by mistake”; back then it was all done by smelling the product and paying cash based on the buyers skill at detecting the cheats followed by CG analysis when they got back to base some weeks later. One sample had 47% so they made the standard inclusive at 48%. The 30% minimum was put there to stop them cheating the other way by diluting with some of the eucalyptus and other oils (including turpentine form the hardware store!).

I spoke to the technician from the Australian Government’s Department of Primary Industry (DPI) essential oil testing facility at Wollongbar, NSW last week asking him what the highest level of T-4-ol he had ever seen in his 15+ years experience as an analytical chemist in a sample of pure Australian TTO. His response: Under a proper distillation regime 42% T-4-ol result is very high and rarely does one see 43% T-4-ol. It is extremely rare to see 45%. I once had a 47% T-4-ol result only to find after a double check from another sample from the same batch that it was a fault in the calibration of the GC unit.

Distillation, June 2012, courtesy of ATTIA

Distillation, June 2012, courtesy of ATTIA

I have never seen a T-4-ol  level in pure TTO to exceed 45%, neither has the analyst from the DPI. When I see the T-4-ol level over 42% I immediately submit it for a chiral test on the assumption that it has been adulterated with T-4-ol which is a waste product from factories that ‘correct’ eucalyptus, sandalwood, tarragon, pine, fennel and aniseed oils. It is also found in turpentine. I would personally like to see the max level dropped to 45%.

It is a myth that higher levels of T-4-ol make TTO more effective. All studies on the efficacy, safety and usage of pure Australian TTO have been conducted using a T-4-ol content of about 40–42%, the level at which it most commonly occurs in plantation sourced oils which have been bred to yield at this level. Australian TTO is a complex mixture of 113+ compounds and it is the synergistic effect of all of these compounds that makes TTO such an effective antibacterial, antifungal and anti-inflammatory product.

Since the mid 1980s there have been many discussions about the optimal levels of T-4-ol and 1,8-cineole in TTO. The fact is that increasing T-4-ol levels above 40% makes no difference to the safety and most importantly the efficacy of Australian TTO. The current demand for T-4-ol levels at around 40% ensures that a sustainable quality of pure, natural TTO can be made available. Demanding T-4-ol levels in excess of 42% will in no way increase the efficacy and safety of TTO; in fact it increases the likelihood of being supplied with an adulterated product contaminated with industrial waste and by-products from other industries where there is no quality assurance, likely resulting in contamination with unknown and untested substances.

I know that some people don’t like standards for natural products, but I believe standardization is a mostly good thing, and certainly for TTO we can see the benefits of ‘fingerprinting” as the analysis and comparison process is sometimes known. I will be publishing a lengthy interview with Tony Larkman in the coming weeks.