Heart Rate Variability Sensing Can Reveal Characteristic Autonomic Modulation via Aromatherapy in Relation to the Effects on Feeling: A Study on Citrus Aurantium Oil and Rose Water

(1) Background: There have been previous reports of autonomic modulation by aromatherapy. In this study, we recorded heart rate variability (HRV) to assess its relationship with the effects on feeling. (2) Methods: Twenty-three healthy subjects, who were blind to the aroma type, were exposed to citrus aurantium oil (CAO) or rose water (RW) aroma for 5 min using a diffuser situated in a room. Electrocardiographic data were measured continuously using a wireless device attached to the chest. R-R intervals were used to calculate HRV scores, including high-frequency (HF) variation, low-frequency (LF) variation, LF/HF ratios, the coefficient of variation in R-R (CVRR), and heart rate. A visual analog scale (VAS) was used to evaluate disfavor, fatigue, anxiety, tension, and somnolence at the end of the treatment. (3) Results: CAO significantly reduced disfavor, anxiety, and tension, while RW did not affect VAS scores. HF scores were high during the treatment with both CAO and RW, indicating parasympathetic activation. Treatment with CAO was also accompanied by an increase in LF and the CVRR, whereas treatment with RW was not. HF scores during CAO treatment were negatively correlated with somnolence. No relationships between VAS scores and HRV scores were observed in the RW treatment. (4) Conclusions: In CAO treatment, parasympathetic activation is related to feeling. RW, on the other hand, exerts its autonomic effects without changes in feeling. These results suggest that autonomic modulation by rose water may not depend on the generated feelings, suggesting the usefulness of HRV monitoring in aromatherapy.