Researchers in Japan recently discovered evidence that lavender and rosemary essential oils may aid the body in defense against oxidative stress, or degenerative activity caused by free radicals. One system of defense the body uses is free radical scavenging activity (FRSA), for preventing biological phenomena such as inflammation, aging and carcinogenesis. The study, “Smelling lavender and rosemary increases free radical scavenging activity and decreases cortisol level in saliva,” used salivary cortisol as an indicator of FRSA.

The subjects, 22 healthy volunteers, sniffed aroma—lavender, rosemary or odorless propylene glycol (as a control)—for five minutes. The aromas consisted of solutions of an essential oil diluted with odorless propylene glycol and propylene glycol alone as a control. The essential-oil solutions were tested in both a low concentration (1,000 times dilution) and a high concentration (10 times dilution).

Saliva from the subjects was collected immediately before the experiment to establish a baseline, and immediately afterward to measure physiologically active substances such as cortisol, secretory immunoglobulin A (sIgA), and a-amylase (a digestive enzyme) activity, which were found to be correlated

Free radical scavenging activity seemed to increase by stimulation with low concentrations of lavender or by high concentrations of rosemary; however, both lavender and rosemary stimulations decreased cortisol levels. Therefore, a significant inverse correlation was observed between the FRSA values and the cortisol levels with each concentration of rosemary stimulation. No significant changes were noted in sIgA or amylase.

It is widely believed that lavender stimulates parasympathetic nerves and helps with relaxation. Rosemary essential oil stimulates the sympathetic nervous system, which can help increase memorizing and concentrating abilities. The data from this study indicates that FRSA can be increased by both sympathetic and parasympathetic actions in the nervous system as a result of aromatherapy. The authors state, “The results of our study on saliva suggest that aroma stimulations with lavender and rosemary may protect the body from oxidative stress by decreasing cortisol and potentiating FRSA.”

Source: Meikai University, School of Dentistry, Saitama, Japan. Authors: Toshiko Atsumi and Keiichi Tonosaki. Originally published in Psychiatry Research, Vol. 150, No. 1, Feb. 6, 2007, pp. 89–96.

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