Why Scientists Are Prescribing Forest Time for Healthier Lungs

Spending time in forests isn't just relaxing—it's actual medicine for your lungs. Scientists have discovered that breathing forest air filled with natural plant compounds called phytoncides can strengthen your immune system, reduce inflammation in your airways, and potentially protect against respiratory infections like COVID-19 and pneumonia.

How Does Forest Air Actually Heal Your Lungs?

When you walk through a forest, you're inhaling invisible compounds that trees release to protect themselves from harmful bacteria and fungi. These biochemical substances, called phytoncides, are made up mainly of terpenes—the same compounds that give forests their fresh, piney smell.

Once you breathe them in, these terpenes can be detected in your bloodstream. Research shows they have antibacterial, antifungal, and antiviral properties that may directly help your body fight off infections, especially in your airways. "These substances can counteract plant parasites, but they are also beneficial for mammals," says Michele Antonelli, who practices preventive and integrative medicine in Reggio Emilia, Italy.

What Specific Benefits Do Your Lungs Get?

Forest bathing triggers several measurable changes in your body that benefit respiratory health:

• Immune Cell Boost: Phytoncides increase the activity and number of natural killer cells, which are white blood cells that attack virus-infected cells in your body
• Inflammation Reduction: Breathing forest air decreases inflammatory molecules called cytokines, which play a key role in lung diseases like asthma and chronic obstructive pulmonary disease (COPD)
• Stress Hormone Drop: Forest time measurably reduces cortisol and adrenaline levels, along with pulse rate and blood pressure, which supports overall immune function

The largest producers of these beneficial compounds are conifers like pines, cedars, and spruce trees. Interestingly, terpene concentration increases with temperature, suggesting that midday forest visits might give you maximum exposure to these healing compounds.

Why Are Doctors Now Prescribing Nature Time?

The evidence is compelling enough that entire countries have adopted forest therapy as official health policy. Japan operates therapy bases in forests across the country as part of a national health strategy, while South Korea runs at least 76 "healing forests" and integrates forest therapy into its National Health Insurance Service.

Even during the COVID-19 pandemic, Italian scientists documented that areas with more trees per capita had lower numbers and severity of COVID-19 cases compared to places with fewer trees, even when accounting for population density differences.

"We should think of the human body not as a collection of separate systems, but like the forest itself—a complex ecosystem with interlinking reactions," explains immunologist Qing Li, who leads the forest research laboratory at the Nippon Medical School in Tokyo and has been conducting field experiments for 30 years.

Beyond the trees themselves, forest environments offer additional respiratory benefits. Waterfalls and fast-moving rivers create aerosolized water that might contain beneficial microbes, while charged ions in the air around moving water may aid your immune system, especially in your respiratory tract. The soil also contributes—microorganisms like Mycobacterium vaccae seem to boost immune function, and the bacterial genus Streptomyces found in forest soil is used in many antibiotics.