19/09/2025
Camping in the forest, or spending time in the forest, a practice known as βforest bathingβ or βshinrin-youβ, has been shown to increase the activity and production of cancer-killing cells, specifically Natural Killer (NK) cells, by as much as 80%.
Phytoncides are antimicrobial organic compounds that trees and plants release to protect themselves from germs and insects. When humans breathe in these compounds, such as alpha-pinene and limonene, the body responds with an increased number of NK cells. These cells are a vital part of the immune system and are responsible for identifying and destroying tumor cells and virus-infected cells.
Studies have found that exposure to phytoncides can significantly increase the levels of intracellular anti-cancer proteins, including performing, granzymes A and B, and granules in, which NK cells use to kill cancer cells. One study even found that simply breathing phytoncides vaporized into a hotel room resulted in a boost of NK cell activity.
Stress hormones like cortisol can suppress the immune system and reduce the function of NK cells. Being in a forest environment has been shown to reduce cortisol levels, allowing the immune system to function more effectively.
The decrease in stress hormones and the increase in NK cells activity appear to work together. Some researchers suggests that the calming atmosphere of forests, combined with the presence of phytoncides, can stimulate both the nervous and endocrine systems to reduce stress and boost immune responses.
Amazingly, the increase in NK cells activity does not disappear as soon as you leave the forest. Studies have found that the boosted immune function can last for more than 7 days and in some cases for up to a month after a forest trip!
PMID: 36417344, 36612777, 36613115, 19568835