Effects of phytoncide on immune cells and psychological stress of gynecological cancer survivors: randomized controlled trials.

This study aimed to identify neuroendocrine substances and natural killer (NK) cells, including their subsets and receptors, to determine whether phytoncides scented in an urban hospital could help improve stress in cancer survivors. Fifty-five gynecological cancer survivors were assigned to either the control group (CG, n=28) or phytoncide group (PTG, n=27). The PTG meditated by lying down in a space scented with phytoncide for 1 hr a day, 5 days a week for 8 weeks. Stress levels in both groups were high prior to the experiment and decreased by 9.31%±45.98% (P=0.003) only in the PTG after the experiment. Although the parasympathetic nerve activity of the PTG increased, the epinephrine and cortisol levels were significantly (P<0.001) decreased by 5.29%±25.5% and by 24.94%±11.62%. Moreover, the PTG showed a significant increase in the levels of NK cell subsets after 8 weeks, whereas there was no improvement in the CG. In conclusion, phytoncide fragrance reduces stress, increases the number of NK cells and their family even in a nonforest environment, and improves innate immunocytes in gynecological cancer survivors; parasympathetic nerve activity and cortisol hormones play critical roles in this process. That is, a phytoncide essential oil helps to stimulate changes in immunocytes' mobility by affecting the human nervous and endocrine systems, thereby providing relief for psychological stress among cancer survivors who previously had cancer cells.