tea tree oil, essential oil derived from the tea tree (Melaleuca alternifolia), a species of tall shrub or tree in the myrtle family (Myrtaceae) originally native to the Bungawalbin Valley in New South Wales, eastern Australia. Tea tree oil historically was used by Australian Aboriginal peoples in herbal remedies. Today, it is commonly used as an over-the-counter topical agent to treat acne, dandruff, athlete’s foot, and various other skin conditions, although there is insufficient evidence to substantiate claims about its effectiveness.
Tea tree oil is derived from the leaves of the plant, being extracted by steam distillation. It is strongly aromatic, having a camphor-like medicinal scent, and ranges from clear to pale yellow in color. The oil is composed of more than 100 chemical compounds, the majority of which are terpene alcohols, such as monoterpenes and sesquiterpenes. The international standard for tea tree oil denotes terpinen-4-ol, a terpineol isomer, as the primary component, and commercially produced oil typically contains 30–40 percent of the compound.
The Bundjalung Aboriginal peoples of northern New South Wales were likely the first to use tea tree plants medicinally. Aboriginal oral history reports stories of “healing lakes” containing fallen leaves of the tea tree plant. Aboriginal peoples most likely employed the plant as an herbal remedy, using inhaled oils from crushed leaves to treat upper respiratory infections and infusions to treat skin conditions. The plant’s medicinal attributes were first documented in the 1920s by Australian chemist Arthur Penfold in a series of papers that explored the germicidal properties of various Australian essential oils. In 1930 the Medical Journal of Australia published an official report on tea tree oil as a potential new germicide. Since then, the oil has been sold in its pure form and included as an ingredient in over-the-counter skin products, including soaps, shampoos, and lotions.
Although tea tree oil is not generally associated with adverse skin reaction, in some persons it can cause skin irritation, which may manifest as itching, burning, or dermatitis at the location where the product was used. Tea tree oil is not intended for ingestion; accidental oral ingestion can cause confusion, loss of muscle control, breathing problems, and coma.