Natural Killer Cells and Forest Bathing

Written By Hugh Asher

19th January 2022

There are a few claims regularly made about Forest Bathing that I was initially a little sceptical about, but that I have now come to recognise as being truthful and supported by overwhelming scientific evidence. Nature Killer (or NK) Cell Activity is one of these.

Image of Natural Killer Cells

Natural Killer Cells

Natural Killer (NK) cells are a type of lymphocyte that serves a variety of function in the immune system, such as destroying infected and abnormal cells in the body. They can even target a viral infection inside cells, without destroying the entire cell.

Stress Reduction and Immune Functioning

Research into Forest Bathing and human immune functioning has suggested that the increase in NK cell activity during forest bathing trips might be caused by a reduction in stress levels. Forest Bathing has been shown to reduce the production of Cortisol, Adrenaline and Noradrenaline and the research proposes that an increase in physical and psychological stress can decrease NK cell activity and that conversely a decrease in the stress hormone Cortisol leads to an increase in NK cell activity.

NK Cells and Forest Bathing

Research has also shown that Forest Bathing enhances NK activity in humans by increasing the number of NK cells and intracellular levels of anticancer proteins. The increased NK activity was shown to last for more than 30 days after a Forest Bathing trip, and this has very important implications for preventive medicine. If the duration of effect is that long, then a monthly Forest Bathing outing should maintain a person’s NK activity level almost permanently.

Taking an urban trip has not been shown to increase human NK activity or numbers of NK cells, indicating that increased NK activity during Forest Bathing is not due to the trip itself but due to the forest environment.

Forest Bathing and Phytoncides

The reason for this is reported to be that trees emit aromatic volatile substances called phytoncides, such as u-pinene and limonene, and these have been shown to significantly increased NK. In most research projects into Forest Bathing the phytoncides were produced by vaporizing Chamaecyparis obtusa (hinoki cypress) stem oil with a humidifier. We stock Hinoki Cypress Essential Oil in our store.

Hinoki Cypress Essential Oil (10 ml) Hinoki Cypress Essential Oil (10 ml)
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Hinoki Cypress Essential Oil (10 ml)
£15.00

10 ml of Therapeutic Grade Hinoki Cypress Essential Oil in a dropper bottle.

Bring the calming scent of the Japanese forest into your home with Hinoki Oil. Distilled from the sacred Hinoki Cypress, this beautifully woody and citrus-fresh essential oil is inspired by the restorative practice of forest bathing and helps create moments of calm, mindfulness, and nature connection.

Hinoki Oil – Bringing the Essence of the Japanese Forest into Your Home

Imagine stepping into a quiet forest of ancient Japanese cypress trees. The air is cool and still. Sunlight filters through the canopy, and the scent of warm wood, fresh needles, and distant citrus fills your senses. This is the experience that Hinoki Oil can evoke.

Distilled from the revered Hinoki Cypress (Chamaecyparis obtusa), a tree that has been treasured in Japan for centuries, Hinoki Oil carries a distinctive aroma that is soft, woody, slightly smoky, and subtly citrusy. Its fragrance is often associated with traditional Japanese temples, forest shrines, and the restorative practice of forest bathing, or Shinrin-yoku.

Many people find Hinoki's scent deeply calming and grounding. Rich in natural plant compounds known as phytoncides, it offers a simple way to bring a little of the forest indoors when spending time among trees is not possible.

Use a few drops in a diffuser during meditation, yoga, journalling, or quiet reflection. Add it to a warm bath to create a spa-like atmosphere, or simply inhale its aroma whenever you need a moment of stillness and reconnection.

At Forest Healing, we love Hinoki because it captures something of the quiet wisdom of old forests. Its scent invites us to slow down, breathe deeply, and remember that we are part of the natural world, not separate from it.

Ways to enjoy Hinoki Oil:

• Diffuse to create a peaceful, woodland-inspired atmosphere
• Add to a nature connection or mindfulness practice
• Blend with cedarwood, bergamot, frankincense, or lavender
• Use as part of an evening wind-down ritual
• Bring the scent of the forest into your home, workspace, or therapy room

A small bottle of Hinoki Oil offers more than a fragrance. It offers an invitation to pause, reconnect, and experience a little of the restorative spirit of the forest wherever you are.

Postage and Packing is £2 for up to six 10ml bottles in the UK.

Due to insurance and liability reasons, we no longer ship our essential oils to the USA or Canada - Sorry!

Soil Microbes and Immune Functioning

Recent research has also shown that exposure to environmental microbes such as those found in healthy soil can boost the human immune system.

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Hugh Asher

I’m Hugh and I’m a Certified Forest Bathing Guide and Forest Therapy Practitioner, having trained with the Forest Therapy Institute and the Forest Therapy Hub. My purpose in life is to inspire people to improve their wellbeing, and to help people to help and inspire others to improve their wellbeing. I do this through promoting greater nature connection as I am a passionate believer in the benefits to health and wellbeing that nature and increased connection to nature can bring.

Professionally, I have worked for over twenty years supporting people experiencing: mental health problems; autism; learning disabilities; school exclusion; experience of the care system; and a history of offending behaviour. Currently I am the ‘Recovery Through Nature Lead’ in a residential rehab for people experiencing drug and alcohol problems.

I have a PhD in Therapeutic Relationships, but Dr. Hugh makes me sound too much like a Time Lord.

https://www.linkedin.com/in/hugh-asher/
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