Japanese Onsen: Bathing Customs, Etiquette and Health Claims
What an onsen is in Japan, common bathing customs and etiquette, which health claims have been studied, and the heat, age and infection cautions that sources describe.
Content last updated . This page has not been medically reviewed.
What an onsen is
Under Japan's Hot Springs Act, as summarised by the Japan Onsen Association, an onsen is water, steam or gas from the ground that is 25 degrees Celsius or more at the source, or that contains a specified amount of at least one of 19 listed substances [3]. A narrower class, the "sanitation spring" from a Ministry of the Environment guideline, is described as one that "can be used particularly for the purpose of cure" [3]. The Association was founded in 1929 and describes its purpose as promoting national health and the use of tourism resources through onsen research [4]. It has an interest in onsen, and the sources we read do not describe it as a regulator.Cultural context
The Association says Japanese people have used onsen for a long time and believe, from experience, that onsen have positive effects on the body [5]. That is a traditional belief, not a trial result. It describes full-body bathing, partial bathing (for example foot or hip baths and pouring water over the neck) and special forms of bathing [5]. For hot-spring geology and other regions see hot springs and thermal baths.Customs and etiquette
One English-language travel guide says practices can differ between establishments [6]. It describes these common customs.- Swimming suits are not allowed in the baths [6].
- Rinse your body well before entering [6].
- Keep the small towel out of the water [6]. The Japan Onsen Association also asks that towels stay out of the bathtub, for water hygiene [7].
- Avoid loud talking, swimming and submerging your head [6].
Rules on tattoos and on mixed or private baths are not described in the sources we read, so check with the facility. Ask staff about anything you are unsure of; this is information, not a list of venues.
Health claims, checked
| Claim | What we found | Strength |
|---|---|---|
| Specific baths help hypertension, insomnia or fatigue | The Japan Onsen Association says lie-down baths are effective for mental fatigue, insomnia, hypertension and arteriosclerosis [5]. It cites no trial on that page. | Traditional use only |
| Onsen bathing helps healthy people | A pilot of 16 healthy men bathing in a sulfur-rich onsen four times over two weeks looked at gut bacteria, with no control group [8]. The paper notes effects in healthy people are not well understood [8]. | Insufficient evidence |
| Warm immersion bathing improves how people feel | A crossover trial of 38 people compared 2 weeks of home immersion bathing with showering, and reported better self-rated fatigue and stress [9]. It tested warm water, not onsen water, and the researchers worked at an onsen research centre [9]. | Promising but limited |
| Mineral baths for arthritis | See balneotherapy trials; reviews rate the evidence weak or insufficient [10][11]. | Mixed |
A 2014 review of 51 spa-therapy trials found many reports left out details such as the qualification and experience of the care provider [12].
Drinking onsen water
Some traditions involve drinking spring water. The Association advises that people under 15 generally avoid it and that people on medicines ask their doctor [13]. Treat drinking as a medical question, not a wellness habit.Infection
Japanese researchers argue that, because onsen bathing is common among older people, strict, enforced regulation and infection control are needed, and that bathing can be a potential cause of Legionella infection [14]. See Legionella in hot tubs and spas.Related pages
Hydrotherapy for older adults, hammam and Turkish baths and hydrotherapy safety.Frequently asked questions
What counts as an onsen?
In Japan's Hot Springs Act, water at 25 degrees Celsius or more at the source, or with listed substances in set amounts [3].
Do you wear a swimsuit in an onsen?
The travel guide we read says swimming suits are not allowed [6]. Rules can vary, so check with the facility.
Is onsen bathing safe for older adults?
It can be risky. Bath-related deaths in Japan are mostly in older people in winter, mostly at home [1][2]. Heart or blood pressure conditions call for medical advice first [7].
Do onsen cure illnesses?
Proper evidence not found. We searched PubMed for onsen and hot spring bathing studies. The claims we read are traditional or from the onsen association [5], and reviews of mineral baths rate the evidence weak or insufficient [10].
Should I bathe alone?
The Japan Onsen Association says children, older adults and people with disabilities should avoid bathing alone [7].
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety first
Cautions from the Japan Onsen Association
- Children, older adults and people with physical disabilities should avoid bathing alone [7].
- Bathing immediately before or after a meal or alcohol should be avoided [7].
- Older people with hypertension or heart disease, and people who have had a cerebral hemorrhage, should avoid water above 42 degrees Celsius [7].
- People with cardiopulmonary insufficiency should prefer hip or partial bathing to full-body bathing [7].
- If you feel faint, leave the bath slowly with your head low and ask for help [7].
The Association also says people with heart disease should be careful about deep, hot baths [5]. The travel guide warns that hot spring bathing can be demanding, especially for people with high blood pressure, and that floors are often slippery and cloudy water can hide steps [6]. It advises avoiding alcohol and drinking water before and after [6]. These are cautions, not a prescription; limits depend on the person. See fainting and low blood pressure after hot water.
References
- Suzuki H et al. Characteristics of sudden bath-related death investigated by medical examiners in Tokyo, Japan. J Epidemiol 2015;25(2):126-132. PubMed 25503827 Read 2026-10-22.
- Katsuyama M et al. Development of prevention strategies against bath-related deaths based on epidemiological surveys of inquest records in Kagoshima Prefecture. Sci Rep 2023;13:2277. PubMed 36754968 Read 2026-10-22.
- Japan Onsen Association. What is onsen? Read 2026-10-22.
- Japan Onsen Association. About the Japan Onsen Association. Read 2026-10-22.
- Japan Onsen Association. Variety ways to take a bath. Read 2026-10-22.
- japan-guide.com. How to take an onsen bath (travel guide, not a medical source). Read 2026-10-22.
- Japan Onsen Association. Caution for using Onsen (for bathing). Read 2026-10-22.
- Takeda M, Choi J, Managi S. Myoban hot spring bathing improves gut microbiota composition and short-chain fatty acid levels: a pilot study. Environ Health Prev Med 2025;30:81. PubMed 41110959 Read 2026-10-22.
- Goto Y et al. Physical and mental effects of bathing: a randomized intervention study. Evid Based Complement Alternat Med 2018;2018:9521086. PubMed 29977318 Read 2026-10-22.
- Verhagen AP et al. Balneotherapy (or spa therapy) for rheumatoid arthritis. Cochrane Database Syst Rev 2015;(4):CD000518. PubMed 25862243 Read 2026-10-22.
- Verhagen A et al. Balneotherapy for osteoarthritis: a Cochrane review. J Rheumatol 2008;35(6):1118-1123. PubMed 18464302 Read 2026-10-22.
- Kamioka H et al. Assessing the quality of study reports on spa therapy based on randomized controlled trials by the spa therapy checklist (SPAC). Complement Ther Clin Pract 2014;20(4):317-333. PubMed 25179406 Read 2026-10-22.
- Japan Onsen Association. Caution for drinking Onsen water. Read 2026-10-22.
- Tanimoto T, Takahashi K, Crump A. Legionellosis in Japan: a self-inflicted wound? Intern Med 2021;60(2):173-180. PubMed 32727982 Read 2026-10-22.