Tea Tree Oil
Tea tree oil has no comedogenicity score in any primary assay we hold — no Fulton row, no Melaleuca row of any kind — and the 1 that circulates online traces to nothing we can find. It rates Clear on the absence of any pore concern in the sources we searched, plus two human acne trials in which it reduced lesions rather than causing them, which is a treatment result, not a comedogenicity measurement.
No assay we can find, and no comedogenic concern on record.
What it is
The essential oil steam-distilled from the leaves and terminal branchlets of the Australian tea tree, Melaleuca alternifolia. On a label it is Melaleuca Alternifolia (Tea Tree) Leaf Oil. It is not a fatty oil in the sense that coconut, olive or jojoba oil are: those are triglycerides and wax esters, liquid fat. Tea tree oil is a volatile mixture of roughly a hundred small terpene molecules, and its composition is pinned by an international standard, ISO 4730 — in the version Carson and colleagues summarised in 2006, it sets minima and maxima for fourteen of them. The dominant component is terpinen-4-ol, required to be at least 30% and usually 30–48% of the oil; then gamma-terpinene and alpha-terpinene, with 1,8-cineole capped low because it is the more irritating fraction. Formulators reach for it as an antimicrobial and anti-inflammatory active in acne and blemish products, not as an emollient — it is doing a pharmacological job, at low percentages, not softening the skin.
Why we rate it Clear
We rate it Clear at LOW confidence, and we hold no legacy score for it, because no primary assay we can trace produced one. Start with what is missing, because the absence is the most useful thing on this page. Tea tree oil does not appear in Fulton's 1989 rabbit-ear table — the 220-row source of nearly every comedogenic number in circulation has no tea tree oil row and no Melaleuca row of any kind. It is not in Fulton's 1984 paper, not in Morris and Kwan 1983, not in Nguyen 2007, not in any of the numeric comedogenicity documents we hold. We identified no comedogenicity assay of tea tree oil, rabbit or human, in the corpus or in the wider literature we searched. The 1-out-of-5 that follows it around consumer charts is not a measurement. It has no primary source we can trace, and it sits in the same column as coconut butter's measured 4 — a row in Fulton's section VI oils, where his asterisk marks a result as depending on the source of the raw material. That is how an untested material comes to look tested and cleared. Our legacy field is blank rather than 1 for that reason. What stands in place of an assay is human data, and it is the reason the Clear is more than a shrug — but it has to be read for exactly what it measured. Two randomised trials put tea tree oil on the faces of people with acne. Bassett and colleagues (Medical Journal of Australia, 1990) ran a single-blind trial in 124 patients, 5% tea tree oil gel against 5% benzoyl peroxide lotion; both arms significantly reduced inflamed and non-inflamed lesion counts — the non-inflamed count is open and closed comedones — with benzoyl peroxide acting faster and more strongly and tea tree oil producing markedly fewer side effects. Enshaieh and colleagues (Indian Journal of Dermatology, Venereology and Leprology, 2007) ran a double-blind, placebo-controlled trial in 60 patients, 5% tea tree oil gel against a vehicle placebo over 45 days; the total lesion count fell from a mean of 21.16 to 11.33 in the tea tree arm, and the gel was 3.55 times more effective than placebo on lesion count and 5.75 times on the acne severity index. Here is the part that governs the rating. Both trials measured treatment — whether an existing crop of acne lesions shrank — not comedone induction, which is what "comedogenic" actually asks. A treatment trial cannot establish that a material is non-comedogenic; a substance could in principle reduce inflammatory lesions while nudging comedone formation, and neither trial was designed to catch that. What the trials do establish is a strong, checkable proxy: tea tree oil was applied at 5% to acne-prone faces, twice daily, for six weeks and longer, and comedone counts went down, not up. That is close to the opposite of what a comedogenic ingredient does. The Clear rests on two things, then, and both are bounded: no source we searched records a pore concern for tea tree oil, and two human trials treated acne-prone skin with it and lesions fell. Neither is a comedogenicity measurement, and we are not going to launder a treatment result into one.
What the evidence doesn’t tell you
Absence of evidence is a weaker thing than evidence of absence, and both halves of that apply here. We found no comedogenicity assay of tea tree oil in the sources we searched, so an absent signal and an absent measurement look identical from here, and the human data we do lean on measured the wrong endpoint for this question — lesion clearance in people who already had acne, not comedone formation in skin that did not. The proxy is strong and it is still a proxy. The more important limit is that Clear here is about pores and nothing else, and tea tree oil does carry a real, well-documented risk — it is simply not a comedogenic one. The oil is irritant and allergenic. Used neat, straight from the bottle, it is one of the more common causes of essential-oil allergic contact dermatitis, and oxidised tea tree oil — oil that has aged in contact with air and light — is a stronger sensitiser than fresh oil, which is why cosmetic safety reviewers ask formulators to protect it from oxidation. A page that rated this ingredient "safe" full stop would be wrong; a page that rates its comedogenicity Clear while saying plainly that its actual hazard is sensitisation is doing the narrower, honest thing. The reader deciding whether to dab it on neat should weigh irritation and allergy, not clogged pores. Two further caveats. "Tea tree oil" names a specification, not a fixed substance: the ISO 4730 spec Carson and colleagues summarised in 2006 allows terpinen-4-ol anywhere from 30% upward and permits a range on every other component, and an oxidised bottle is chemically not the fresh oil the trials used — and we found no comedogenicity assay of any of those variants. And the trials behind the proxy are modest: 124 and 60 patients, one single-blind and one double-blind, both testing a 5% gel formulation rather than the ingredient alone, neither counting comedone induction as an endpoint. They are real human evidence pointing one way. They are not a comedogenicity study, and we found no comedogenicity study to put beside them.
Where you’ll see it
On a label it appears as Melaleuca Alternifolia (Tea Tree) Leaf Oil, and in related forms as Melaleuca Alternifolia Leaf/Terminal Branch Oil. It turns up in spot treatments, blemish gels, acne cleansers and toners, "natural" and "clarifying" skincare lines, and in scalp and foot products, and it is also sold on its own as a neat essential oil that people dilute themselves. The clinical studies that support it used it at around 5%; the anti-acne positioning is precisely why people paste it into a comedogenic checker and are then surprised to find it has no score. That it is marketed as an acne treatment does not by itself make it non-comedogenic — but it does mean the material has been tested on acne-prone skin more than most, and that testing did not turn up a pore-clogging problem.
Sources
Each source says what it actually is. Several widely-cited “sources” for comedogenic ratings are republishing the same 1989 assay, and counting them as independent agreement is how a thin evidence base gets made to look thick.
- Fulton JE. "Comedogenicity and irritancy of commonly used ingredients in skin care products." J Soc Cosmet Chem 40:321–333 (1989) The primary 0–5 rabbit-ear assay behind nearly every comedogenic score online, including the scores on this site. Method: ingredient at roughly 10% in propylene glycol, applied to the inner ear of New Zealand albino rabbits, three rabbits per assay, follicles scored for keratosis. Cited here for a negative, and it is the load-bearing fact on the page: the 220-row table contains no tea tree oil row and no Melaleuca entry of any kind. There is no Fulton score for tea tree oil to republish, which is why the 1 that circulates cannot be traced to him, or to any primary source we searched.
- Carson CF, Hammer KA, Riley TV. "Melaleuca alternifolia (Tea Tree) Oil: a Review of Antimicrobial and Other Medicinal Properties." Clin Microbiol Rev 19(1):50–62 (2006) The standard peer-reviewed review of the oil, from a University of Western Australia group that has published extensively on tea tree oil. Cited for composition, not comedogenicity: it sets out the ISO 4730 specification as it stood in 2006 (fourteen components, terpinen-4-ol the major one at roughly 30–48%, 1,8-cineole held low), and it documents the oil's dermal tolerability — irritant and allergenic potential, and the fact that oxidised oil is a more potent sensitiser than fresh. It says nothing about comedogenicity or pores; it is the source for what the material is and for its actual documented risk, which is sensitisation.
- Enshaieh S, Jooya A, Siadat AH, Iraji F. "The efficacy of 5% topical tea tree oil gel in mild to moderate acne vulgaris: a randomized, double-blind placebo-controlled study." Indian J Dermatol Venereol Leprol 73(1):22–25 (2007). PMID 17314442 A randomised, double-blind, placebo-controlled trial in 60 patients, 5% tea tree oil gel against a vehicle placebo over 45 days, with total lesion count and acne severity index as endpoints. The tea tree arm's mean total lesion count fell from 21.16 to 11.33, and the gel was 3.55 times more effective than placebo on lesion count and 5.75 times on severity. Characterised precisely: this is a TREATMENT-efficacy trial measuring the reduction of existing acne lesions, not a comedogenicity study measuring comedone induction. Cited as the strongest human proxy we have, and only as a proxy — it did not, and could not, establish non-comedogenicity.
- Bassett IB, Pannowitz DL, Barnetson RS. "A comparative study of tea-tree oil versus benzoyl peroxide in the treatment of acne." Med J Aust 153(8):455–458 (1990). PMID 2145499 A single-blind randomised trial in 124 patients comparing 5% tea tree oil gel with 5% benzoyl peroxide lotion. Both significantly reduced inflamed and non-inflamed (comedone) lesion counts; benzoyl peroxide acted faster and more strongly, and tea tree oil produced markedly fewer side effects. Cited alongside Enshaieh as the second human trial on acne-prone faces — and, like it, characterised as a treatment trial, not a comedogenicity assay. Single-blind, not double-blind, and testing a 5% gel rather than the neat ingredient.
- Hammer KA. "Treatment of acne with tea tree oil (melaleuca) products: a review of efficacy, tolerability and potential modes of action." Int J Antimicrob Agents 45(2):106–110 (2015). PMID 25465857 A review of the acne-treatment evidence and tolerability, by a researcher whose group specialises in tea tree oil — an affiliation worth stating. Cited for the tolerability synthesis across trials: the side effects reported for tea tree oil acne products are typical of topically applied acne treatments and occur at similar or lower rates, and human patch-test studies show real but low rates of irritant and allergic reaction. Relevant to the limits section, not to a comedogenicity score, which the review does not provide.
Others in the same family
Botanical extracts behave similarly enough that the evidence for one is often wrongly read across to the others. These are its structural relatives, not a guess. What the evidence says about botanical extracts as a family ›
Last reviewed 2026-08-12 · How we decide