The Onsen Ritual: Japan's Ancient Practice of Hot Spring Healing

There are approximately 25,000 hot spring sources throughout Japan, and roughly 3,000 onsen establishments use naturally hot, geothermally heated water from these springs. The practice of bathing in them is not a wellness trend — it is a 1,300-year-old tradition so deeply woven into Japanese culture that it has its own word for therapeutic immersion: tōji (湯治), the practice of staying at an onsen for a week or more to treat illness and restore health.

Historical records show that onsen bathing has existed in Japan since at least the Nara period (710–794 CE). Many of the earliest records document Japanese emperors and members of the imperial family staying at onsen for extended periods, seeking cures for disease. At the time, hot springs were considered sacred, imbued with healing properties by the kami (spirits) that inhabited them. The oldest onsen in Japan — Dōgo Onsen in Ehime Prefecture, Shirahama Onsen in Wakayama Prefecture, and Arima Onsen in Hyōgo Prefecture — each claim histories stretching back well over a millennium (en.wikipedia.org/wiki/Onsen).

Until around the Edo period (1603–1868), onsen maintained close religious ties to Buddhism, with temples frequently built near hot spring sources. Monks believed the hot waters were a gift from the Buddhist deity Yakushi Nyorai, the Buddha of medicine and healing. During the Edo period, however, onsen culture shifted. Depicted in ukiyo-e woodblock prints by masters like Hokusai and Hiroshige, hot springs became destinations not just for the religious and the ill, but for ordinary people seeking cleanliness, socialising, and the simple pleasure of a good soak. The onsen boom of the 1980s bubble economy cemented hot spring tourism as one of Japan's most beloved forms of domestic travel (nippon.com).

The science behind onsen therapy is more robust than one might expect. Japan's Hot Spring Act, administered by the Ministry of the Environment, classifies onsen waters by their mineral composition — and each classification carries documented therapeutic properties. Simple thermal springs relax muscles and improve circulation. Sulphur springs are believed to help with cardiovascular conditions. Carbon dioxide springs dilate blood vessels, lowering blood pressure. Iron-rich springs are said to benefit anaemia, while radium springs — yes, trace amounts of naturally occurring radiation — are thought to stimulate the immune system. The Onsen Medical Science Research Center at Beppu University has spent decades studying these effects, documenting improvements in everything from stiffness and swelling to skin conditions like psoriasis and eczema (onsen-msrc.com).

A peer-reviewed study published in the journal Health & Place by researchers Mihaela Serbulea and Unnikrishnan Payyappallimana examined onsen as 'therapeutic landscapes,' concluding that the practice of tōji — the extended stay at a hot spring for healing — represents a sophisticated integration of terrain, water, community, and ritual that modern medicine is only beginning to appreciate. The study, cited over 100 times, highlights how onsen transform physical geography into healing landscapes, blending the mineral properties of the water with the psychological benefits of retreat, nature, and community (doi.org/10.1016/j.healthplace.2012.06.020).

The onsen ritual itself is governed by a precise etiquette that is itself a form of mindfulness. Before entering the bath, you must shower thoroughly — sitting on a low stool at a row of taps, washing every part of your body with the provided soap, shampoo, and rinse bowl. Only when you are impeccably clean do you approach the bath. You carry only a small modesty towel (often placed on your head), which must never touch the bath water. You enter slowly, lowering yourself into the steaming pool with deliberate care. Talking is kept to a murmur. Swimming is forbidden. The water is often quite hot — 40 to 111°F (104–111°F) — and the practice is to soak for short intervals, perhaps five to ten minutes at a time, stepping out to cool on a rock or under a cold shower before re-entering. This contrast between hot and cold is itself therapeutic, stimulating circulation and promoting what the Japanese call 'totonou' — a state of harmonious balance between body and mind.

For the traveller seeking to experience onsen, Japan offers an extraordinary range. Beppu, on the southern island of Kyushu, is perhaps the most famous onsen city in the world, with eight distinct 'hells' (jigoku) — boiling pools of various mineral compositions and vivid colours that are too hot for bathing but are among Japan's most spectacular natural phenomena. The nearby Takegawara Onsen, built in 1879, offers traditional sand baths where attendants bury you in naturally heated black volcanic sand. Hakone, within easy reach of Tokyo, offers mountain onsen with views of Mount Fuji. Kinosaki Onsen in Hyōgo Prefecture is a charming town of seven public bathhouses linked by a willow-lined canal, where guests stroll between baths in cotton yukata robes and wooden geta sandals. Noboribetsu in Hokkaido is surrounded by volcanic hell valleys and offers some of Japan's most mineral-rich sulphur waters.

The ryokan — Japan's traditional inn — is where the onsen experience reaches its fullest expression. A night at a quality ryokan includes a kaiseki dinner of perhaps a dozen seasonal courses, a morning feast of grilled fish, rice, and miso soup, a futon laid out on tatami matting, and most importantly, access to the onsen at any hour. The best ryokan have both indoor and outdoor (rotenburo) baths, gender-separated, and many offer private baths (kashikiri) that can be reserved. The experience of soaking in an open-air onsen as snow falls gently around you, or as the dawn light breaks over a misted mountain valley, is one of the most profound experiences of stillness available in the modern world.

What makes onsen culture so relevant to the modern wellness conversation is its refusal to separate the physical from the spiritual, the individual from the community, or the body from its environment. An onsen is not a treatment you receive — it is a practice you enter. The minerals in the water matter, but so does the quality of the light, the sound of the river, the cedar of the bathhouse, the conversation (or silence) of fellow bathers, and the deliberate slowness of the ritual. In a world that increasingly treats wellness as an optimisation problem — something to be hacked, measured, and completed — the onsen offers something older and perhaps wiser: the understanding that healing is not a destination but a practice, and that the waters have been waiting for far longer than we have been seeking.

For those planning a visit, the Japan National Tourism Organization provides comprehensive guidance on onsen etiquette, regional guides, and accessibility information (jnTO.go.jp). The Japan Spa Association maintains a registry of certified onsen establishments and offers detailed information on water compositions and therapeutic classifications (spa.or.jp). And for those who wish to understand the medical science, the Onsen Medical Science Research Center at Beppu University publishes research in both Japanese and English (onsen-msrc.com).