Safety assessment and adverse drug reaction reporting of tea tree oil (Melaleuca aetheroleum)

Tea tree (Melaleuca alternifolia) essential oil is widely used as an antiseptic. It mainly consists of monoterpenes with terpinen-4-ol as the major constituent. The aim of this study was to review literature on safety data about tea tree oil and to assess its safety by investigating 159 cases of adverse reactions possibly caused by the oil, reported to the World Health Organization (WHO) from December 1987 until September 2021. To extract these data, VigiBase, the WHO global database of individual case safety reports maintained by the Uppsala Monitoring Centre (UMC), was used. All cases were categorized and analysed and 16 serious cases further assessed. It was concluded that tea tree oil should never be administered orally, as it can lead to central nervous system depression and pneumonitis. Applied topically, skin disorders may occur, especially when the oil had been exposed to light or air. This yields monoterpene oxidation products, being potent skin irritants. Tea tree oil stored under appropriate conditions and not exceeding the expiration date should be considered safe to use by non-vulnerable people for non-serious inflammatory skin conditions, although the occurrence of adverse reactions such as contact allergies is difficult to predict.

Automated summary

Tea tree essential oil, mainly consisting of monoterpenes, is commonly used as an antiseptic. This study reviewed safety data and analyzed cases of adverse reactions reported to the WHO. The findings suggest that oral administration of tea tree oil can lead to central nervous system depression and pneumonitis, while topical application may cause skin disorders. Properly stored tea tree oil within its expiration date is considered safe for non-serious inflammatory skin conditions, but the occurrence of adverse reactions is difficult to predict.