Suppression of tumor necrosis factor-alpha-induced neutrophil adherence responses by essential oils.

BACKGROUND In aromatherapy, essential oils are used as anti-inflammatory remedies, but experimental studies on their action mechanisms are very limited. AIMS To assess their anti-inflammatory activities, effects of essential oils on neutrophil activation were examined in vitro. METHODS Neutrophil activation was measured by tumor necrosis factor-alpha (TNF-alpha)-induced adherence reaction of human peripheral neutrophils. RESULTS All essential oils tested at 0.1% concentration suppressed TNF-alpha-induced neutrophil adherence,and, in particular, lemongrass, geranium and spearmint oils clearly lowered the reaction even at 0.0125%. Similar inhibitory activities for the neutrophil adherence were obtained by their major constituent terpenoids: citral, geraniol, citronellol and carvone. In contrast, very popular essential oils, tea tree oil and lavender oil, did not display the inhibitory activity at the concentration. CONCLUSION Thus, some essential oils used as antiinflammatory remedies suppress neutrophil activation by TNF-alpha at a low concentration (0.0125-0.025 %) in vitro.