Objectives: People have been aware of essential oils, which are derived from plants, for a long time. Recently, we have become interested in physiological and subjective effects of daily exposure to essential oils. The primary aim of the present study was to clarify effects of olfactory stimulation with rose or orange oil on prefrontal cortex activity; subjective evaluations of relaxation were also determined.
Setting and interventions: Subjects were exposed for 90s to air impregnated with either rose or orange essential oil. As a control, subjects wore the same device but inhaled only unimpregnated air. The three stimuli were randomly presented to each subject.
Main outcome measures: Physiological effects were determined by near-infrared time-resolved spectroscopy and a modified semantic differential approach was used to determine subjective evaluations.
Results: The study participants were 20 female university students (mean age 22.5±1.6 years). Olfactory stimulation by rose or orange oil induced: (1) a significant decrease in oxyhemoglobin concentration in the right prefrontal cortex and (2) an increase in "comfortable," "relaxed," and "natural" feelings.
Conclusion: These findings indicate that olfactory stimulation by rose or orange oil induces physiological and psychological relaxation.
Keywords: Near-infrared spectroscopy; Orange; Physiological relaxation; Rose; Semantic differential method.
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