BACKGROUND: The aim of this study was to determine the effects of out-door activities in the forest environment, the so-called "forest therapy program," among children with atopic dermatitis (AD).METHODS: A total of 40 children with moderate-severity AD were enrolled in this study. All subjects were divided into either the "forest group" participating in the forest therapy program or the control group. The vitamin D level and quality of life (QOL) were measured at the initial visit and 8-week final visit.RESULTS: The SCORing Atopic Dermatitis (SCORAD) index was reduced significantly more in the forest group than in the control group (39.17±4.48 vs. 27.00±4.87); however, it did not reach statistical significance. The vitamin D (25(OH)-D₃) level was increased significantly more in the forest group than in the control group (p>0.001). The mean QOL score was not significantly decreased in the forest group.CONCLUSION: The forest therapy program was proven to be associated with the reduction of the SCORAD index and the increase of vitamin D level. However, QOL measures did not show statistically significant improvement. Thus, the forest therapy program may have a positive trend of biological and psychosocial effects in children with AD.