this ref looks interesting
(3.) Stromkins J. The Autonomic Nervous System and Aromatherapy. Chelsea Printers, Richmond, BC.
The hypothesis is sandalwood oil causes a decrease in sympathetic tone as accessed with patients by the Heart Rate Variation (HRV), blood pressure (systolic, diastolic, and pulse pressure) and pulse rate.
Sandalwood oil’s effect on the autonomic nervous system Original Internist - Find Articles