Spilling The Tea on Tea Tree Oil

Dear Valerie: I keep hearing that “tea tree oil is tea tree oil” when it comes to formulations, but I’ve also heard that quality can vary significantly depending on origin and processing. Does this really affect finished product performance? If so, what should formulators ask suppliers to ensure the oil is high quality, traceable to its source, and likely to deliver the efficacy reported in studies?

—SPILL THE TEA

Dear Spill, 

Tea tree oil and I go way back, and my journey involves my mentor Dr. Ron DiSalvo and stories with names like B.J. Thomas and Sir Jason Winters, author of the text “Breakthrough. In Search of An Australian Legend: Miracle Healing Oil of the Ages.” Looking back, it sounds like the beginning of a strange dinner party.

Many of you know I spent a large portion of my career working on a certain tingly tea tree shampoo, which meant we bought (and tested) a lot of tea tree oil. So, “Spill The Tea,” you have come to the right chemist. I have, quite literally, spent years investigating what was in the tea.

If there is one thing I can state with confidence, it’s that the notion “tea tree oil is tea tree oil” is about as accurate as saying “wine is wine.” Not convinced? Try a glass of Boone’s Farm Strawberry Hill, then a glass of Austin Hope Cabernet and tell me, with a straight face, that “wine is wine.”

The commercial tea tree oil industry originated in Australia, but one can find TTO in other parts of the world as a result of globalization. TTO is an essential oil typically steam distilled from the Melaleuca alternifolia plant, and contains a complex mixture of monoterpenes, sesquiterpenes, their associated alcohols, and many more molecules. 

Why I disagree all tea tree oils are created equal, is that—with any premium essential oil—there is economic incentive to drizzle in cheaper materials to dilute the cost. TTO is also easy to fake. Adulterers can easily take synthetically produced terpenes, or extractions from similar-chemistry plants like eucalyptus, and dilute the tea tree oil with it, cutting an expensive oil to form a cheap oil.

The International Organization for Standardization (ISO) published its standard for tea tree oil, “Oil of Melaleuca, terpinen-4-ol type (tea tree oil),” or ISO 4730. An important quality benchmark for TTO, which inherently offers a glimpse into TTO’s authenticity, the standard outlines several requirements in its current edition, including organoleptic and physical properties, but also GC profile requirements for various molecules like limonene, p-cymene, 1,8-cineole and terpinen-4-ol.

Although there is variation in plant materials, Australian tea tree oil is pretty predictable when it comes to what’s in it, and how much is in it. In my opinion, the ISO standard is an important accountability metric to producers. The SCCS in the EU also now considers the standard important, but for a different reason—safety.

However, while ISO compliance is an important quality benchmark, it isn’t necessarily proof of authenticity. Meaning, just because a TTO follows the ISO standard, doesn’t mean it can’t be a good fake. A 2024 article published in the Journal of Agricultural and Food Chemistry¹ found that following the ISO standard didn’t necessarily reveal when TTO was adulterated. Adulterers can add synthetic (or other) materials in quantities that push the oil to the edges of, but within, the ISO standard specification range. Essentially, even with these adulterants, the GC chromatogram can lead one to believe the tea tree oil tested is authentic.

What is much harder to fake, however, is chirality. As I mentioned, real tea tree oil is predictable in a lot of ways, and one of them is the ratios of enantiomers it produces. For example, the tea tree plant consistently churns out (+)-terpinen-4-ol and (-)-terpinen-4-ol, in roughly a 70-30 ratio. A good supplier of authentic tea tree oil knows this is important and will report the ratio values on their certificates of analysis. If your supplier isn’t reporting enantiomeric data on the COA, ask whether they test it and request the results. Its absence from a COA doesn’t necessarily mean the supplier is up to something nefarious, but I was trained under the notion that if it wasn’t written down, it wasn’t done.

Now, does this “variation” in quality matter? If you value TTO for its efficacy but are unknowingly purchasing what you think is TTO (but isn’t), I think it’s safe to say efficacy could be impacted, and this is a huge problem. Using a known composition, such as one that follows the ISO standard and is real tea tree oil, is important from a safety standard. I also think adulterated and oxidized TTO can smell like a dirty old canvas bag of coins, but that’s neither here, nor there.

At the end of the day, tea tree oil needs substantiation of authenticity. Buy from quality suppliers who know their source, understand their analytical data and are willing to share it.  It’s no good to buy raw materials from companies who knowingly (or worse, unknowingly) sell something that’s not what it says it is. This is why I spent an unreasonable amount of my professional life figuring out whether the TTO was indeed TTO.

For more answers to your questions from Valerie George, click here.

Valerie George

[email protected]

Valerie George is a cosmetic chemist, science communicator, educator, leader, and avid proponent of transparency in the beauty industry. She works on the latest research in hair color and hair care at her company, Simply Formulas, and is the co-host of The Beauty Brains podcast. You can find her on Instagram at @cosmetic_chemist or showcasing her favorite ingredients to small brands and home formulators at simply-ingredients.com

References

1. Linge, Kathryn L., Leif Cooper, and Angela Downey. “Comparison of Approaches for Authentication of Commercial Terpinen-4-ol-Type Tea Tree Oils Using Chiral GC/MS.” Journal of Agricultural and Food Chemistry, vol. 72, no. 15, 2024, pp. 8389–8400.