---
title: "How to bathe in an onsen: Japan's hot-spring rules, from washing first to tattoos"
description: "At a Japanese onsen you undress completely, wash before getting in and keep your towel out of the water. What makes water an onsen, the board in the changing room, mixed bathing and tattoos."
url: https://kama-meshi.com/en/articles/onsen-basics
language: en
published: 2026-11-11
category: "Travel basics › Everyday Japan"
tags: ["Onsen"]
author: "Oginoya Editorial Team"
publisher: "Oginoya Co., Ltd."
translations:
  zh-TW: https://kama-meshi.com/zh-tw/articles/onsen-basics
  ko: https://kama-meshi.com/ko/articles/onsen-basics
  zh-CN: https://kama-meshi.com/zh-cn/articles/onsen-basics
  zh-HK: https://kama-meshi.com/zh-hk/articles/onsen-basics
  th: https://kama-meshi.com/th/articles/onsen-basics
  de: https://kama-meshi.com/de/articles/onsen-basics
  fr: https://kama-meshi.com/fr/articles/onsen-basics
  es: https://kama-meshi.com/es/articles/onsen-basics
---

# How to bathe in an onsen: Japan's hot-spring rules, from washing first to tattoos

![An open-air bath edged with boulders below a green forest, with a wooden roof over one corner and water pouring in from a bamboo pipe](https://kama-meshi.com/_astro/nigorigo-onsen-rotenburo-2018.COlAuQXe_1fYyUX.webp)

At an onsen, a Japanese hot spring, bathers leave all their clothes, swimsuits included, in a changing room for their own sex, and they wash at a washing station and pour hot water over themselves before stepping into the bath. The small towel stays out of the water, long hair is tied up, and no one swims, splashes or brings a phone or camera into the bathing area.

## What makes water an onsen

Japan's Hot Springs Act of 1948 defines an onsen as hot water, mineral water, steam or other gas that comes out of the ground and passes either of two tests: a temperature of at least 25°C when drawn from its source, or a set amount of any one of 19 substances listed in the law, such as 1,000 milligrams of dissolved substances other than gases, or 1 milligram of sulfur, in a kilogram of water. Water colder than 25°C can therefore be an onsen by law.

At the end of March 2025, Japan had 2,839 onsen areas, counting only places with lodging, and 27,899 hot-spring sources. Hokkaido had the most onsen areas, 226, and Oita Prefecture the most sources, 5,094.

## Before getting in

Changing rooms are separate for men and women, and so are almost all baths. Shoes or slippers come off before the changing room, and all clothing stays there. A small towel, usually provided, may be held in front of the body on the way to the bath.

The bathing area has washing stations, each with a stool, a bucket and often a hand-held shower. Bathers wash sitting down and rinse off every trace of soap. Before getting into the bath, they also pour hot water over themselves, from the hands and feet to the whole body. This is *kakeyu*, and it lets the body adjust to the heat so that blood pressure does not rise suddenly. Many baths have a basin near the entrance for it.

![A square stone bath of clear water around a round stone column that pours hot water, below a blue-and-white tile mural of two herons between a pine and a willow, with showers and buckets along the side walls](https://kama-meshi.com/_astro/dogo-onsen-kaminoyu-bath-2017.Dov2VkpZ_1m9OPz.webp "Kami-no-Yu, a bath in the main building of Dōgo Onsen, Matsuyama, 2017. Dōgo is said to be the oldest hot spring in Japan.")

## In the water

The towel never goes into the bath, which keeps the water clean; bathers fold it and rest it on their heads or on the edge of the bath. People speak quietly, and taking photographs in the bathing area is strictly forbidden, out of respect for other bathers' privacy, particularly that of minors.

## What the board in the changing room says

Every facility that offers onsen water for public bathing must post the water's components, the conditions under which bathing is contraindicated, and cautions for bathing. Since an amendment of 2007, the analysis behind the board must be redone at least every ten years. If the water has been diluted, heated, recirculated, given additives or disinfected, the board also says so and why.

![Two printed sheets pinned to a weathered white board: on the right a table headed 温泉分析書 with the spring's temperature and contents, on the left a sheet headed 中之郷尾越温泉スタンド listing indications, contraindications and cautions](https://kama-meshi.com/_astro/hachijojima-onsen-analysis-2008.Dt2eInm7_Z1dlAGp.webp "The analysis of a spring on Hachijōjima, Tokyo, posted at a stand where people draw the water for their baths at home, 2008. It gives a temperature of 53.1°C and classes the water as a sodium chloride spring.")

The contraindications and cautions follow a national standard, last revised in 2014. The contraindications for any onsen include bleeding, severe disease of the heart, lungs or kidneys, and the active phase of an illness, especially with a fever. Acidic and sulfur springs are also contraindicated for people with sensitive skin.

The cautions advise against bathing just before or after a meal or after drinking alcohol, and recommend drinking water before and after the bath. Older people and people with high blood pressure or heart disease are to avoid water of 42°C or more. The cautions put a soak at three to ten minutes until the bather is used to the water, and 15 to 20 minutes after that. Afterward, onsen water is patted off with a towel rather than rinsed away, except by people with sensitive skin after a strongly acidic or sulfur spring.

## Open-air baths and mixed bathing

A *rotenburo* is a bath in the open air, and an *uchiyu* is a bath inside [an inn](https://kama-meshi.com/en/articles/what-is-a-ryokan), with water piped in from the spring.

*Kon'yoku*, mixed bathing, went on in public bathhouses until late in the Edo period (1603–1868). The Kansei Reforms of 1787–93 ordered it stopped, and the Meiji government banned it again in 1869–70. Under the national hygiene guidelines for public bathhouses, males and females aged about seven and over do not bathe together; until December 2020 the age was about ten.

## Tattoos

Some traditional onsen do not admit bathers with tattoos, and many provide or sell cover sheets, which suit only very small ones. In March 2016 the Japan Tourism Agency told four associations of hotels, ryokan and hot springs that refusing someone a bath only because of a tattoo was not appropriate. Among the points it asked them to keep in mind were that people wear tattoos for religious, cultural and fashion reasons, and that a tattoo causes no problem of hygiene.

The agency asked each facility to work out its own approach and listed examples: covering the tattoo with a sticker; asking nothing special of a small tattoo, about the size of a palm, that does not intimidate other bathers; suggesting hours when few families are bathing; and offering a separate bath, a *kashikiriburo* (private bath) or a guest room with its own bath. Two days later the Ministry of Health, Labour and Welfare asked prefectures, major cities and Tokyo's special wards to make sure that bathing facilities refused no one on unjust grounds.

## Ten types of spring

Onsen with qualities useful for therapy are classed as *ryōyōsen*, "therapeutic springs," in ten types set by temperature or main components: simple, chloride, hydrogen carbonate, sulfate, carbon dioxide, iron, acidic, iodine, sulfur and radioactive springs. Small bubbles cling to the body in a carbon dioxide spring, iron springs turn golden in the air, and iodine springs turn yellow when left standing. A strongly acidic spring stings the skin and tastes sour; the water of [Kusatsu Onsen](https://kama-meshi.com/en/articles/kusatsu-onsen) in Gunma is around pH 2.0.

## Onsen and sentō

An onsen is defined by its water, and a *sentō* by its business: a bathhouse open to anyone for a fee. Sentō come under the Public Bathhouse Act, also of 1948, which covers facilities where the public bathes in hot water, onsen water and the like. Under that law, bathers must not make the bath markedly unclean, and operators must turn away anyone with an infectious disease. At the end of March 2025, 7,721 public bathhouses in Japan used onsen water.

## References

- [e-Gov Laws, "Hot Springs Act (Act No. 125 of 1948)"](https://laws.e-gov.go.jp/law/323AC0000000125)
- [Ministry of the Environment, "Recent hot-spring administration: outline of the Hot Springs Act" (PDF)](https://www.env.go.jp/content/000062656.pdf)
- [Ministry of the Environment, "Hot spring use in fiscal 2024 (as of March 31, 2025)" (PDF)](https://www.env.go.jp/nature/onsen/pdf/6-7_p_1.pdf)
- [Ministry of the Environment, "Safe and secure hot-spring use: the basics" (March 2019, PDF)](https://www.env.go.jp/nature/onsen/pdf/top.pdf)
- [Japan National Tourism Organization, "How to Best Enjoy Japan's Onsen"](https://www.japan.travel/en/guide/how-to-best-enjoy-onsen/)
- [Ministry of Health, Labour and Welfare, "On bathing by foreign visitors with tattoos" (March 18, 2016, PDF)](https://www.mhlw.go.jp/content/11130500/001361312.pdf)
- [Chiba Prefecture, "Age limit for mixed bathing at public bathhouses"](https://www.pref.chiba.lg.jp/eishi/koushuueisei/sonohoka/konyokunenreiseigen.html)
- [Kotobank, "Onsen"](https://kotobank.jp/word/%E6%B8%A9%E6%B3%89-41936)
- [Kotobank, "Kon'yoku"](https://kotobank.jp/word/%E6%B7%B7%E6%B5%B4-506793)
- [Kotobank, "Sentō"](https://kotobank.jp/word/%E9%8A%AD%E6%B9%AF-154531)
- [Kotobank, "Rotenburo"](https://kotobank.jp/word/%E9%9C%B2%E5%A4%A9%E9%A2%A8%E5%91%82-663841)
- [Kotobank, "Uchiyu"](https://kotobank.jp/word/%E5%86%85%E6%B9%AF-440625)
- [Town of Kusatsu, "About Kusatsu Onsen"](https://www.town.kusatsu.gunma.jp/s013/040/020/1485254967207/index.html)

Image credits (resized for display):

- [Alpsdake / Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Outdoor_hot_spring_bath_in_Nigorigo_Onsen.jpg), [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0), 2018
- [松山市役所 / Wikimedia Commons](https://commons.wikimedia.org/wiki/File:%E3%80%90%E6%B5%B4%E5%AE%A4%E3%80%91%E7%A5%9E%E3%81%AE%E6%B9%AF%E7%94%B7%E6%9D%B1%E6%B5%B4%E5%AE%A4.jpg), [CC BY 4.0](https://creativecommons.org/licenses/by/4.0), 2017
- [Soica2001 / Wikimedia Commons](https://commons.wikimedia.org/wiki/File:Nakanogo_Onsen_Bunsekisyo.jpg), Public domain, 2008