Shinrin-Yoku, translated from Japanese, as “forest bathing” suddenly became “a thing” to me after I heard it mentioned at a tree care seminar earlier this year. The term then started popping up over the following few months.

It refers not to washing in a forest stream or lake, but immersing oneself in the atmosphere in a forest.

It brings to mind the days we spent as kids, riding bikes through the woodsy portions of Dry Creek and Redwood Road on the outskirts of Napa, and playing in the creeks.

It seems I always felt energized and happy outside among the trees.

Now there is a term for it and scientists are studying the health benefits resulting from breathing in volatile substances given off by trees and other plants.

Looking into the topic, I found Shinrin-Yoku was formally developed in Japan during the 1980s and has become a well-recognized practice for good mental, emotional and physical health.

Relaxation and a feeling of well being come on easily and quickly, at least for me, just being among plants and trees. I have heard this from others, most frequently in reference to walking among ancient coast redwoods. People often describe it as a feeling of peace or reverence.

Aside from the mental and emotional aspect of walking in a forest, there is evidence that volatile organic compounds emitted by trees can have direct, disease-preventative effects for people.

On the negative side, air pollution caused by trees has been in the news, and it is documented in the literature: trees exude volatile materials, which oxidize in sunlight and become haze, as in the Blue Ridge Mountains, or smog in urban areas that have lots of internal combustion vehicles and lots of certain tree species.

Trees are mighty factories for a huge array of phytochemicals, some of which science has yet to understand as to function.

In “Physiology of Woody Plants” (1979) the authors state “The essential oils have no known essential functions in plant metabolism although they may be useful in attracting pollinators or repelling predators”.

They go on to say “Many of the compounds synthesized by plants, especially terpenes and alkaloids, have few known functions. On the other hand, considerable attention has been given to the possible protective functions of phenolic compounds and other compounds against pathogens and insect pests.”

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Taking a leap beyond that, scientists have been looking at volatile phytochemicals having disease prevention and curative effects for people.

In 1928, Dr. Boris P. Tokin, a Russian biochemist from Leningrad University, coined the term “fitonsid”, translating to English as “phytoncide,” for chemicals given off by some plants that inhibit decay and insect attack. The term means “exterminated by the plant.”

In a paper titled “The Effects of Phytoncides on Natural Killer Cells in Humans” author Denell Nawrocki (find her at states “Phytoncides… are active substances that are anti-bacterial, anti-fungal, and anti-viral … They are produced and emitted from trees to protect them from harmful insects, animals, and germs. Phytoncides give a forest environment its quintessential ‘forest smell’ (they) have an effect on human physiology as well…We can speculate that forest environments may have beneficial effects on the human immune system by reducing stress and affecting immune-cell production and function.”

Nawrocki cites studies of the effects of forest bathing, and simulated forest bathing, where analysis of things like T-cell and NK-cell function indicate phytoncides bolster the human immune system.

I find these ideas intriguing, even though the science of it has a long way yet to go.

In any case, a walk in the woods will do you good.

Bill Pramuk is a registered consulting arborist. Visit his website, Email questions to or call him at 707-226-2884.