Long before "tea tree oil" showed up on skincare aisle labels everywhere, Australian researchers put it head-to-head against a proven acne treatment in a real clinical trial. The 1990 study, published in the Medical Journal of Australia by Bassett, Pannowitz, and Barnetson, remains one of the most cited pieces of evidence for tea tree oil's use on skin.
It may have been three decades ago, but it’s worth looking at because it’s studies like these that set the path for ingredients and in this case, prove their legitimacy as effective solutions to problems. Additionally, in the three decades since, much more research has firmly established the medicinal benefits of tea tree and it’s active Terpinen-4-ol.
Why Tea Tree Oil?
Tea tree oil is extracted from Melaleuca alternifolia, a tree native to Australia that has high levels of the bioactive Terpinen-4-ol. For years leading up to this study, it had been used informally as a topical antiseptic, and lab studies had confirmed it has genuine antimicrobial properties. But antiseptic activity in a test tube doesn't prove a product works on real skin conditions and at the time, its use for acne was based on anecdote rather than evidence. This trial set out to test that gap directly.
The Study
Researchers ran a single-blind, randomised clinical trial on 124 patients with mild to moderate acne. Participants were split into two groups: one applied a 5% tea tree oil gel, the other a 5% benzoyl peroxide lotion. Benzoyl peroxide being a standard, well-established acne treatment. Patients were tracked over time, and researchers counted both inflamed lesions (like pimples) and non-inflamed lesions (blackheads and whiteheads).
What They Found
Both treatments worked. Tea tree oil and benzoyl peroxide each significantly reduced the number of acne lesions compared to baseline. The main differences were speed and side effects. Benzoyl peroxide started working faster, while tea tree oil took longer to show its full effect.
The more notable finding was on tolerability. Patients using tea tree oil reported fewer side effects than those using benzoyl peroxide, an important detail, since benzoyl peroxide is well known for causing dryness, redness, and skin irritation, which is a common reason people stop using it.
What It Means
The takeaway from this trial is that tea tree oil is a legitimate, evidence-backed option for mild to moderate acne, not just a folk remedy. It's slower to act than benzoyl peroxide, but is a gentler, natural approach for those looking to avoid chemicals and reduce unwanted side-effects.
In recent years there has also been research demonstrating that Benzoyl Peroxide turns into benzene, a known carcinogen, when exposed to heated environments. This resulted in many acne products getting recalled and a reasonable concern over using such harsh chemicals in skincare products.
Knowing tea tree is effective also offers a synthetic chemical free solution to acne treatment, helping to reduce chemical load on the body which in these times of chemical overload is an increasingly important factor. In addition, it guides formulations–any tea tree acne leave-on treatment worth its salt should be using 5% tea tree to be effective.
As with any single trial, there are caveats. The sample size (124 patients) is respectable but modest, the study was single-blind rather than double-blind, and formulations of both products have evolved since 1990. Still, this study helped move tea tree oil from anecdote to genuine clinical evidence, and it's a big part of why it remains a common ingredient in acne treatments today.
Source: Bassett IB, Pannowitz DL, Barnetson RS. "A comparative study of tea-tree oil versus benzoylperoxide in the treatment of acne." Medical Journal of Australia, 1990;153(8):455–458.
