Encyclopedia · botanical
Tea tree oil
A popular natural dandruff remedy with modest evidence, whose oxidised oil is a well-documented contact allergen.
What it is
Tea tree oil is an essential oil from the Australian plant Melaleuca alternifolia, rich in terpinen-4-ol. It is sold as a cosmetic ingredient and added to shampoos.
What the studies show
Our search surfaced reviews of essential oils as candidate dandruff treatments (Kumari 2022; Jain 2022), but we did not open a primary dandruff trial, so we do not state a trial effect size. Benefit is plausible, small and based on limited trials.
On safety, a review of contact allergy found that fresh oil is a weak sensitiser but oxidation raises its allergenicity. The main sensitisers include ascaridole, terpinolene and alpha-terpinene. Reactions mostly came from the pure oil, and the oil can cross-react with turpentine and fragrance. The suggested patch test is 5% oxidised oil (de Groot 2016).
Side effects and safety
Allergic contact dermatitis is the main risk, especially with old or oxidised oil. Never apply it undiluted, keep it away from eyes, and store it tightly closed away from light and heat.
Bottom line
Tea tree oil is reasonable as an add-on in a ready-made shampoo, and a poor do-it-yourself choice for sensitive or allergy-prone scalps. For proven results use ketoconazole or zinc pyrithione.
Studies 3
de Groot AC. Tea tree oil: contact allergy and chemical composition. 2016
Result: Fresh tea tree oil is a weak sensitiser but oxidation raises allergenicity; major sensitisers include ascaridole, terpinolene and alpha-terpinene; reactions mostly came from pure oil; it cross-reacts with turpentine and fragrance.
Read the study ↗Kumari KMU et al. Promising Essential Oils/Plant Extracts in the Prevention and Treatment of Dandruff Pathogenesis. 2022
Result: Review of essential oils and plant extracts as candidate anti-dandruff agents.
Read the study ↗Jain S et al. Essential Oils as Potential Source of Anti-dandruff Agents: A Review. 2022
Result: Review of essential oils as candidate anti-dandruff agents.
Read the study ↗Related
- Rosemary oilRosemary oil became the internet's "natural minoxidil" from one small 2015 trial that had no placebo group and has never been replicated.
- Zinc pyrithioneThe most widely used anti-dandruff shampoo ingredient, proven in large trials to cut flaking, though most of those trials were run by the companies that sell it.
- DandruffDandruff is a common, chronic flaking of the scalp driven by yeast, skin oil and your skin's sensitivity, and an antifungal shampoo controls it well as long as you keep using it.