2018 Volume 23 Issue 1 Pages 9-15
Many medical professionals have shown an interest in the clinical use of essential oils (EOs) for their analgesic and sedative effects. However, the main side effects of EOs are skin irritation and sensitization, and their frequency and severity have not been clarified. This paper describes the results of the comparison of skin sensitization reactions of three essential oils containing linalool using an in vitro sensitization test (human cell line activation test, h-CLAT). The h-CLAT method quantifies the expression levels of monocyte and cluster of differentiation (CD) cell surface markers (CD86 and CD54) in a THP-1 human monocytic leukemia cell line after EO exposure. The test oils were bergamot EO (BEO), Ho leaf EO (HLEO), and thyme linalool EO (TLEO). The dose-finding assay showed the estimated concentration required to elicit 75% cell viability (CV75) of TLEO to be 96.3 µg/mL while values were not obtained for BEO and HLEO at up to 1000 µg/mL. All EOs induced skin sensitization as revealed by CD54 values. Therefore, skin sensitization induced by EO mixtures could be confirmed using h-CLAT.