Melaleuca alternifolia (Maiden & Betche) Cheel

M. linariifolia var. alternifolia Maiden & Betche

Australian tea tree; ti tree

Myrtaceae

Melaleucae alternifoliae aetherolium

Essential oil, extracted by steam distillation of the leaves and terminal branches (twigs)

There is variability in the chemical profile of tea tree oil and six chemotypes (varieties) of M. alternifolia are recognised, each with a distinct chemical composition. The most highly valued varieties contain at least 40% terpinen-4-ol. There is an international standard that stipulates ranges for 14 constituents of the oil, including terpinen-4-ol, terpinene, terpinoline, cineole, terpineol, cymene, pinene and limonene. The composition of the oil may alter considerably during storage, as its stability is affected by light, heat, air and moisture (Carson et al. 2006; Tisserand and Young 2014).

Clinical studies assessing the efficacy of tea tree oil in the treatment of acne have demonstrated that 5% tea tree oil reduces the number of inflamed lesions on a par with benzoyl peroxide, but with significantly fewer side effects (Carson et al. 2006).