Abstract

Phytoncides and forest volatile organic compounds (VOCs) have gained increasing attention in discussions of forest bathing, forest therapy, and nature-based health promotion. Yet the term phytoncides is often used imprecisely, obscuring both its historical origins and its broader ecological and chemical significance. This article examines phytoncides and forest VOCs from an interdisciplinary perspective, integrating their conceptual development, chemical diversity, ecological functions, environmental variability, and possible relevance to human health. It begins by revisiting the origins of the phytoncide concept in plant antimicrobial defense and situates it within the wider framework of biogenic volatile organic compounds emitted by forest ecosystems. The article then outlines the major chemical families associated with phytoncidal activity, including terpenes, terpenoids, phenylpropanoids, green leaf volatiles, sulfur-containing compounds, and less volatile resinous or phenolic defenders, emphasizing how molecular structure shapes volatility, reactivity, and biological action.

The discussion further considers forest VOCs as dynamic components of therapeutic environments rather than static chemical features. In this context, recent work on the evaluation of forest therapy environments is examined alongside evidence for seasonal and geographical variation in phytoncide and VOC concentrations across different forest types and climatic regions. These findings suggest that the atmospheric qualities of forest environments are temporally variable and influenced by species composition, canopy structure, temperature, radiation, humidity, and local microclimate, with important implications for the planning of guided Shinrin Yoku and forest therapy sessions.

Finally, the article reviews current evidence on the relationship between forest VOC exposure and human health, including pharmacokinetic observations, possible effects on inflammation, immune activity, stress physiology, mood, and nervous-system regulation. While several forest VOCs, particularly monoterpenes such as limonene and α-pinene, show plausible anti-inflammatory, immunomodulatory, and neuropsychological potential, the current evidence does not support reducing the benefits of forest exposure to VOC inhalation alone. Rather, forest VOCs are best understood as one dimension of a broader multisensory and ecological therapeutic context. The article concludes that phytoncides and forest VOCs provide an important bridge between plant science, ecology, and forest therapy, while also requiring careful interpretation, methodological rigor, and resistance to overly reductionist claims.