Physiological effects of inhaling fragnances

Abstract

To clarify whether or not inhaling fragnance of lavender, rosemary or citronella affects physiological conditions, responses of the autonomic nervous system were evaluated by measuring R-wave intervals on an electrocardiogram, blood pressure, blood flow in the fingertip and galvanic skin conductance. Heart rate variability was also examined using spectral analysis. Lavender was the most effective fragnance in terms of eliciting calmness and relaxation. When inhaled for 10 minutes, lavender produced an increase in blood flow and decrease in galvanic skin conductance and systolic blood pressure, indicating a reduction in sympathetic nerve activity followed by decreased blood pressure. Rosemary, which is perceived as having a refreshing effect, decreased blood flow and increased systolic blood pressure immediately after inhalation, resulting from stimulating sympathetic nerve activity. Citronella produced an increase in R-R interval on the electrocardiogram and decreased blood flow and galvanic skin conductance. The high frequency component of spectral analysis, which reflects only parasympathetic nervous activity, was significantly increased following inhalation of lavender or citronella. The ratio of the low frequency/high frequency components, which reflects an autonomic balance, was increased significantly by rosemary or citronella inhalation, indicating that sympathetic nervous activity had become predominant. These results suggested that fragnances that cause feelings of calmness or relaxation, such as lavender, produce a relaxed condition in the autonomic nervous system by increasing parasympathetic whilst depressing sympathetic nervous activity in addition to mental or psychological effects. In contrast, refreshing fragnances, such as rosemary, stimulate sympathetic nervous activity. Citronella seems to activate both para-sympathetic and sympathetic nervous activity. Appreciation of citronella varies widely among individuals, which might be associated with its complex effects on the autonomic nervous system.