Some of the best things for your health are free. One of them is as simple as a walk in the woods. The Japanese call it shinrin yoku, or "forest bathing": a slow, mindful visit to a forest where you take in the atmosphere through all your senses. It's been described as a kind of natural aromatherapy, and the research behind it is remarkable.
Here's what forest bathing is, what science says about its benefits, and how the plant compounds you breathe in among the trees may strengthen your immune system and calm your mind.
What Is Forest Bathing?
Forest bathing isn't hiking or exercise. It's simply being in a forest: walking slowly, sitting, breathing deeply and noticing the sights, sounds and smells around you. The practice was developed in Japan in the 1980s as a public health measure and has since been studied extensively by Japanese researchers. A 2022 review in *Environmental Health and Preventive Medicine*, Effects of forest environment (Shinrin-yoku/Forest bathing) on health promotion and disease prevention, summarizes decades of this work.
What Are Phytoncides?
The key to forest bathing's benefits appears to be phytoncides, sometimes called "wood essential oils." These are natural compounds that trees and plants release into the air to protect themselves from insects, bacteria and fungi. Many phytoncides are terpenes, including:
- Alpha-pinene: the fresh scent of pine
- Beta-pinene
- Limonene: also found in citrus peel
- Camphene
When you walk among trees, you breathe these volatile compounds in.
Forest Bathing Benefits for the Immune System
More natural killer (NK) cells
Natural killer cells are white blood cells that seek out and destroy virus-infected cells and tumor cells. In a series of studies led by Dr. Qing Li of Nippon Medical School, forest bathing trips significantly increased both the number and activity of NK cells (Int J Immunopathol Pharmacol, 2007). Participants also had higher levels of the anti-cancer proteins perforin, granulysin and granzymes inside those cells.
The effect lasts
In a follow-up study, the boost in NK activity lasted more than 7 days after the trip, and in some participants up to 30 days. The researchers suggested that a forest bathing trip about once a month could help keep NK activity elevated.
It's the forest, not just the vacation
To test whether a relaxing trip anywhere would do the same thing, researchers compared a forest visit with a city sightseeing trip. Only the forest trip increased NK activity (Visiting a forest, but not a city, increases human natural killer activity).
Phytoncides alone have an effect
In a lab study, simply exposing immune cells to phytoncides from trees increased NK cell activity. That suggests the compounds in forest air play a direct role.
Forest Bathing Benefits for Mental Health
Lower stress hormones
Forest bathing trips significantly lowered urinary levels of the stress hormones adrenaline and noradrenaline (Environ Health Prev Med, 2010), a sign that participants were physiologically less stressed.
Less anxiety, depression and anger
Participants in forest bathing studies report lower scores for anxiety, depression, anger and fatigue, and higher scores for vigor (Environ Health Prev Med, 2022).
Better sleep
Research in *Experimental Neurobiology* found that phytoncides have sleep-enhancing effects in animal models. That supports what many forest bathers report: they sleep better after time among trees.
How to Practice Shinrin Yoku
- Find a forest, park or tree-lined trail. Even an urban park with mature trees counts.
- Leave the phone in your pocket. Turn off notifications.
- Slow down. Walk aimlessly and slowly, or find a spot to sit.
- Engage your senses. Notice the smell of pine and soil, the sound of leaves and birds, the feel of bark and moss.
- Breathe deeply. This is how you take in the phytoncides.
- Stay a while. Studies often used two-hour sessions, but even 20 to 30 minutes is a good start.
- Make it a habit. Aim for regular visits, ideally at least once a month.
Bring the Benefits Home
You can't bottle a forest, but plant compounds can still be part of your daily routine. Essential oils from plants such as lavender, chamomile and conifers carry many of the same aromatic terpenes. Our guide Does Aromatherapy Work? What the Research Says explores how breathing in plant compounds affects mood, stress and sleep.
To build a nightly ritual, try the Calm-Soothe-Sleep Magnesium Body Butter. It combines lavender essential oil with magnesium in a nourishing blend of plant oils and butters to help you unwind before bed. Explore the full Calm, Soothe & Sleep collection.
So don't just stop and smell the roses. Stop and smell the trees.
FAQs: Shinrin Yoku
What does shinrin yoku mean?
"Shinrin" means forest and "yoku" means bath, so shinrin yoku translates to "forest bathing," or immersing yourself in the forest atmosphere.
What are the main benefits of forest bathing?
Research links forest bathing to increased natural killer cell activity, lower stress hormones, reduced anxiety and depression scores, and better mood and sleep.
How long should you forest bathe?
Many studies used sessions of about two hours, but even 20 to 30 minutes in a green space can help you relax.
References
- Effects of forest environment (Shinrin-yoku/Forest bathing) on health promotion and disease prevention. *Environ Health Prev Med.* 2022.
- Li Q, et al. Forest bathing enhances human natural killer activity and expression of anti-cancer proteins. *Int J Immunopathol Pharmacol.* 2007.
- Li Q. Effect of forest bathing trips on human immune function. *Environ Health Prev Med.* 2010.
- Li Q, et al. Visiting a forest, but not a city, increases human natural killer activity. *Int J Immunopathol Pharmacol.* 2008.
- Li Q, et al. Effect of phytoncide from trees on human natural killer cell function. *Int J Immunopathol Pharmacol.* 2009.
- Sleep-enhancing Effects of Phytoncide Via Behavioral, Electrophysiological, and Molecular Modeling Approaches. *Exp Neurobiol.* 2020.