Introduction Stress-related disorders, such as depression, psychosomatic disorders and anxiety neurosis, are common and increasing in the workplace. Aromas have ataractic and sedation effects on the parasympathetic nerves. They also affect the feelings of fatigue from stress by stimulating the central nervous system. The purpose of this study is to examine the effect of an olfactory stimulus on changes in a physiological index. Using aromas during the loading of stress, we measured beat-to-beat interval (R-R interval) times from electrocardio-gram (ECG) recordings.

Methods The subjects in our study were 3 male medical university students (subjects’ codes were A, B and C). After assuming a relaxed seated position for 10 min, the subjects performed a mental arithmetic task for 60 min followed by relaxation for 30 min, and then a rest for 10 min. The mental arithmetic task is a method of adding numbers without using tools. Every subject performed both the control-load and aroma-load tests under the same protocol, while the ECG was measured. They smelled lavandula angustifolia during the aroma-load.

Result We analysed the power spectrum of high and low frequencies. The P1 (low frequen-cy)/P2 (high frequency) was defined as the ratio of P1 to P2. There was no change in the P1/P2 of 2 out of 3 subjects by using the aroma. Subjects A and B could avoid mental stress by using the aroma during the mental arithmetic operation.

Discussion In an analysis of the power spectrum in the R-R interval times, the high and low frequencies in the physiological index of stress loading suggest that the aromas have an effect on the autonomic nervous system. As the strain on sympathetic nerve was relaxed, we conclude that the aroma affected the sympathetic nerves. Thus, we conclude that the aroma affected a sympathetic nerve, relaxing the strain on it.