Alleviation of the acute stress response following mild orange essential oil administration

Abstract

We investigated the effect of two different concentrations of orange aroma on peripheral and cardiac autonomic nervous system activity under a stressful condition in a highly reproducible manner. In the within‐subjects experiment, 19 subjects performed a 30‐min calculation task under three aroma conditions: 1% orange, 20% orange, and scentless air (control). Each aroma was delivered to the subject intermittently with the use of a proprietary olfactometer in a counter‐balanced order. Along with a visual analog scale (VAS), nose tip temperature and the cardiac activity on electrocardiograms were recorded throughout the experiment. Regardless of the aroma condition, significant decreases in nose tip temperature and the high‐frequency (HF) component of heart rate variability (HRV) and a significant increase in heart rate (HR) were observed during the task, denoting a typical acute stress response. However, the increase/decrease in HR and HF were significantly smaller with 1% orange than with 20% orange and the control condition, indicating an inhibition of sympathetic nervous system elevation and parasympathetic nervous system suppression. There were no significant differences between the two doses for the VAS scores. The findings suggest that mild orange essential oil inhalation inhibits the cardiac stress response while demonstrating no significant effect on subjective stress. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.