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Due to the lack of antiseptics with sporicidal properties, the activity of tea tree oil (TTO)-containing products was investigated according to the EN 14347 European suspension method. The activity of different concentrations of TTO in 0.001% Tween 80, as well as an alcoholic hygienic skin wash (AHSW) and an alcoholic handrub (AHR), was compared to the sporicidal disinfectants sodium hypochlorite (SH) and hydrogen peroxide (HP), and the antiseptic povidone iodine (PVI). These formulations were assessed after 30, 60 and 120 minutes against two strains of spore-forming bacteria: Bacillus cereus and Bacillus subtilis . The TTO formulated products and PVI did not achieve >4 log 10 reduction in spore counts, thus did not meet the European standard requirements. Nevertheless, 5%, 10% and 15% TTO in 0.001% Tween 80 significantly reduced the concentration of bacterial spores when compared with the water control, and were generally more effective than PVI. At a concentration of 15%, TTO was more active than 0.05% SH against spores of both strains after 30 minutes' contact time, while 5% TTO in Tween 80 was generally more active than the AHSW that also contained 5% TTO. These findings emphasise the fact that it is necessary to assess final formulations rather than the active component by itself as excipients may interfere with the activity. The alcohol-containing AHSW and AHR did not demonstrate any sporicidal properties, confirming previous studies showing that alcohol is not sporicidal and suggesting no synergy between TTO and alcohol against spores. Hence these should not be used for hand hygiene or surface decontamination if spores are involved. Further studies should be carried out to investigate the potential sporicidal activity of TTO directly on human skin in vivo with volunteers andlor by using an ' ex vivo ' test that uses freshly excised human skin and which would allow testing of any biocide as well as any spore-forming bacterial strain, including pathogens.

Complementary and alternative medicines occupy a privileged marketing position in many countries, including Australia, being able to carry low-level health claims while being relatively unfettered by regulatory requirements. Consequently, many enjoy widespread use for therapeutic purposes in the absence of definitive efficacy or safety data. Occasionally, the therapeutic properties of complementary and alternative medicines are scrutinised more closely and more thoroughly than their conventional counterparts, leading to the confirmation or discrediting of their properties.