“ #Pine, #cedar, and #cypress #trees release compounds called #phytoncides to defend themselves from insects and bacteria. You breathe them in, and Li believes they switch your immune cells into high gear.

He estimates one forest walk a month may be enough to keep those cells elevated all year.

The best #medicine might not even need a prescription -- just a walk among the trees.”

https://pmc.ncbi.nlm.nih.gov/articles/PMC2793341/