An evaluation of the mutagenic potential of commercially available tea tree oil in the United Kingdom

An investigation of the in vitro mutagenic potential of a variety of commercially available and widely used tea tree essential oils was performed. The mutagenic potential of tea tree oil (Melaleuca alternifolia) was examined using the Histidine Reversion Assay (Ames Test). One of the major components, the monoterpenoid terpinen-4-ol, was also examined to determine if it demonstrated any mutagenic potential. Salmonella typhimurium (TA102, TA100 and TA98) was utilised in the Ames test. Commercially available tea tree oils were tested. Despite a previous report demonstrating a possible mutagenic trend in a single commercially available tea tree product, no mutagenic effect was determined in any of the brands of tea tree oil on any of the strains of Salmonella examined with or without metabolic activation. The same negative results were obtained for the terpinen-4-ol component examined. There was a clear evidence of toxicity of tea tree oil on all Salmonella strains and also by terpinen-4-ol at higher dose levels. It is suggested that terpinen-4-ol may contribute significantly to the widely reported antibacterial activity of tea tree oil.