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Tea tree oil

Tea tree oil in skincare: Antimicrobial essential oil. What it does on skin, how strong the evidence behind the claim actually is, the concentrations in normal use, who reacts to it, and where it stands in pregnancy and sunlight. On a label it appears as Melaleuca Alternifolia (Tea Tree) Leaf Oil.

Soothers, protectants and acne activesAntimicrobial essential oilEvidence: Limited

On the label: Melaleuca Alternifolia (Tea Tree) Leaf Oil. Also called: Melaleuca oil.

This is an ingredient reference, not a diagnosis and not a treatment plan. It describes what substances are and what the published evidence supports; it does not tell you what your skin has or what to put on it. A rash that spreads, hurts, weeps, does not settle, or comes with feeling unwell is a reason to see a doctor or pharmacist, not to change serum.

What it is

The steam-distilled essential oil of an Australian tree, a mixture of dozens of terpenes of which terpinen-4-ol is the main active. It is genuinely antimicrobial, which is unusual among botanical ingredients, and it is also one of the more common plant-derived causes of allergic contact dermatitis — both of those facts are well documented and both belong on the label.

What it does on skin

It has antibacterial and antifungal activity in the laboratory, and it is used at low concentrations in acne products, scalp products and antiseptic preparations. Its terpenes also carry an irritant potential of their own, so the concentration that kills organisms and the concentration that irritates skin are much closer together than they are for a purpose-made pharmaceutical.

What the evidence is worth

Evidence: Limited

Limited. The best-known clinical work is a small Australian trial published in 1990 comparing a 5% tea tree oil gel with 5% benzoyl peroxide for acne, which found tea tree oil acted more slowly but caused fewer side effects. That is a single small study from decades ago, and the body of evidence has not grown into anything decisive since. It is a plausible mild option, not an equivalent to a proven treatment.

How it is used

Diluted, at around 5% or less, in a purpose-made product rather than mixed at home from a bottle of neat oil. Store it dark, closed and cool, and replace it when it is old — this is the ingredient where storage genuinely changes the risk. Never apply neat oil to broken skin.

Typical concentration in normal use: 5% or less in cosmetics. That is a description of the market, not a recommendation, and it is not a dose.

Who reacts to it

Allergic contact dermatitis is well recognised and is driven largely by oxidation: exposed to air and light, the oil forms peroxides and other degradation products that are far more sensitising than the fresh oil. Old, half-used bottles are the classic culprit. Undiluted application is irritating to almost everyone.

Pregnancy and breastfeeding

Needs a conversation

There is little safety data on tea tree oil in pregnancy, and essential oils in general are an area where evidence is thin. Occasional low-concentration topical use is unlikely to be a problem, but this is worth raising with your midwife rather than assuming.

Sunlight

No change

Not typically photosensitising itself. Some other essential oils are strongly photosensitising — expressed citrus oils such as bergamot are the classic example — so "essential oil" is not a category with one answer.

Rules and labelling

Permitted in cosmetics, with limits on the tolerated peroxide content of the raw material because of the oxidation problem. Several of its terpene components are on the EU list of fragrance allergens that must be named individually on the label above set thresholds.

What it goes with, and what it does not

It does not need to be combined with anything, and it should not be added to a routine that already contains a retinoid or an acid on the same area. If acne is the target, benzoyl peroxide or a retinoid is the better-evidenced choice and a pharmacist can advise.

One thing people get wrong

The myth is that being natural makes it gentle. Tea tree oil is a potent mixture that ranks among the more frequent plant contact allergens, and its allergenicity increases the longer the bottle has been open. It is also toxic if swallowed — ingestions in children are a real reason poison centres get called — so it should be stored like a medicine, out of reach.

Sources: EU Cosmetics Regulation (EC) No 1223/2009 and its annexes, as published in the European Commission's CosIng database, for every statement about what is permitted, restricted or banned · opinions of the Scientific Committee on Consumer Safety (SCCS) and safety assessments of the Cosmetic Ingredient Review (CIR) for the concentration positions · standard dermatology reference material for mechanism, tolerability and contact-allergy patterns · checked 2026-09-06. Deep links are deliberately omitted where a stable public URL could not be confirmed.

Frequently asked questions

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