Expert Column: Getting Ready for the Summer Heat — A Fermentation Bath as Summer Preparation

By Prof. Kazunori Ito
Professor, Faculty of Acupuncture and Moxibustion, Meiji University of Integrative Medicine / Director, Japan Enzyme Bath Association

Every month, Hakkou Ningen and Prof. Kazunori Ito publish a column on the enzyme bath — also called a fermentation bath — from the perspective of Eastern medicine and yojo, the Japanese tradition of everyday self-care. This is the English version of the July column, written as Japan’s rainy season gave way to full summer.

Not just cooling down, but warming and balancing

Many people believe that the way to get through summer is simply to keep the body cool. From the perspective of Eastern medicine, however, what matters more is to “warm and balance” the body.

In Japan, the weeks when the rainy season ends and full summer begins are said to be a time when dampness lingers in the body after long days of rain, and when the body’s natural flow tends to slow down. Add strong sunshine and air conditioning, and the body quietly builds up fatigue. It becomes easier to drift toward small, vague signals — feeling sluggish, having less appetite — a state Eastern medicine calls mibyo: not illness, but not quite full health either.

The accelerator and the brake

Behind these ups and downs is the autonomic nervous system. It is the system that keeps the body in balance without our thinking about it, through two sides: the sympathetic nervous system, which drives activity (the accelerator), and the parasympathetic nervous system, which invites rest (the brake).

In summer, as we move back and forth between hot streets and cold indoor rooms, the body has to switch between accelerator and brake again and again. In car terms, the engine tends to run a little overheated. That is why taking time to warm the body slowly from deep inside, and to let it shift into “rest” mode, is said to be a foundation for feeling steady through the summer heat.

A fermentation bath as summer preparation

This is where we suggest a fermentation bath (enzyme bath), which uses the heat created as rice bran and sawdust ferment. Unlike hot water, the soft warmth of fermentation reaches slowly into the core of the body. Guests warm up gradually and break into a gentle sweat, and in Eastern medicine this kind of slow warming is thought to help restore the body’s natural flow.

• No need to go every day. Try it when you feel tired, or on a weekend after a week of air-conditioned chill — whatever you can manage is enough.
• Rest afterwards. After the bath, have a cup of plain warm water and take your time to relax.
• Enjoy how it feels. Savoring that comfortable feeling is the best way to keep it up.

If you have a medical condition, or on days when you don’t feel well, please don’t push yourself, and talk to your doctor first.

Summer yojo is subtraction, not addition

Getting through summer is not about working hard to add something new. It is about subtracting the fatigue and chill that have built up, and letting the body return to its own natural rhythm. Keep warming yourself gently, at your own pace, without overdoing it. That is the first step toward feeling steady even in the hottest weather. This summer, why not quietly add a fermentation bath to your life as a comfortable way to prepare for the season?

This column shares general ideas from Eastern medicine and the Japanese tradition of yojo. It is not medical advice, and experiences vary from person to person. The original column was written in Japanese for the Japan Enzyme Bath Association.

About Prof. Kazunori Ito

Prof. Ito is a professor in the Faculty of Acupuncture and Moxibustion at Meiji University of Integrative Medicine in Nantan, Kyoto, and a director of the Japan Enzyme Bath Association. He has spent many years in research and education in Eastern medicine, and works with Hakkou Ningen on joint research into the enzyme bath and on academic conference presentations.

Bringing the enzyme bath to your country

Guests come back to the enzyme bath for the experience itself: deep, enveloping warmth that comes only from fermentation, the scent of wood and rice bran, and a one-to-one welcome from staff. At our own shops in Japan, around 90% of guests return — yet outside Japan, an authentic enzyme bath is still rare.

It is also a business that cannot be started just by buying tubs and materials. The heat comes from living microbes, and fermentation shifts with the climate, the building, the materials and the season. When it is not managed well, the bath will not warm up, odors appear and guests stop coming. That is why learning from people who actually run enzyme baths matters.

Hakkou Ningen has supported more than 80 enzyme bath openings across Japan — from snowy Hokkaido to subtropical Okinawa — and we are now preparing our first overseas shop in Los Angeles. You train hands-on for 7 days in a working shop in Miyama, Kyoto, and we can help you set up fermentation in your own climate, with materials shipped from Japan (where quarantine rules allow) or sourced locally. Our baths are known for their low odor — we have installed them in hotels, salons and even apartment rooms, and none of the shops we have supported has had to close because of odor. It is not a franchise: you open under your own name. And through our work with Prof. Ito, we keep studying the enzyme bath together with a Japanese university.

Thinking about offering an enzyme bath in your country? Message us on WhatsApp to get our free program guide — pricing, a business simulation and the full training curriculum — or visit our opening program page.