Tea tree oil

What it is

Tea tree oil is steam-distilled from the leaves of Melaleuca alternifolia, a small tree native to Australia. Its main active compound, terpinen-4-ol, kills a wide range of bacteria and fungi and calms inflammation in laboratory tests, which is why it turns up in acne gels, washes and spot treatments. It is a potent essential oil, not a gentle plant extract.

What the evidence says

Evidence: moderate. Two randomised trials found that a 5% tea tree oil gel reduced acne spots, one against benzoyl peroxide and one against placebo; both studies are small.

In a 1990 single-blind trial of 124 people with mild to moderate acne, 5% tea tree oil gel reduced both inflamed spots and blackheads about as well as 5% benzoyl peroxide, although it worked more slowly and caused fewer side effects¹. A 2007 double-blind trial of 60 people found a 5% gel was several times more effective than placebo at cutting the total number of spots over 45 days². A 2015 review brought together the handful of clinical trials of tea tree oil acne products and the laboratory work on how it might act³; the trials remain few and small. The NIH's complementary health centre is more cautious and calls for more research⁴. Nothing suggests it helps deep, cystic acne. Our natural acne care guide shows where it fits in a routine.

How people use it

• A ready-made gel, cream or wash with around 5% tea tree oil, applied to clean skin once or twice daily over the whole acne-prone area.
• If diluting pure oil yourself, use about one drop in a teaspoon (5 ml) of a plain carrier such as jojoba oil or aloe gel, which gives roughly 1 to 2%.
• Introduce it on its own and give it 8 to 12 weeks before judging it. For shine and blocked pores more generally, see oily skin and clogged pores.

Cautions

• Never use it neat. Applying undiluted essential oils can sensitise you, and once you are allergic the reaction tends to return with every exposure⁵. Patch test any product on the inner arm twice a day for seven to ten days.
• Old oil is worse. Oil exposed to air, heat or light oxidises, and oxidised components are more likely to cause redness and allergy^{4, 5}. Keep bottles capped, dark and cool, and replace them yearly.
• It is poisonous if swallowed, causing confusion, unsteadiness and even coma⁴. Keep it away from children and pets.
• Stop if you get itching, scaling or spreading redness, and ask a pharmacist or doctor. See when to see a dermatologist if a reaction does not settle.