What is an Onsen?

Onsen 温泉, pronounced as “oun-saen,” is a widely-known term related to relaxation in Japan, and is the local name for hot spring. It is a source of hot water baths located in different parts of Japan, usually situated around a volcanic area. An onsen was originally found outdoors with no need of material construction, flowing with steam in natural locations. It has later evolved into features of ryokans where the meaning also ranges, referring to accommodations like resorts, hotels, and facilities. It comes in different types, taking forms of shapes and materials it is made from, like cypress wood, granite, marble, and other stones. The reason for the populous number of hot springs is because the country has so many passive and active zones of volcanoes.
Onsen in N. Japan Yamagata An outdoor onsen, also known as rotenburo, in the Yamagata Prefecture


History of Onsen

The term “onsen” was first mentioned in the Japanese book of chronicles “Kojiki", also referred to as “Furukotofumi” during the 8th century. This is considered the earliest history book in Japan, where legend states that hot springs can heal up to 40,000 diseases. According to the onsen tradition of the Japanese, the roots of hot springs trace back to Shintoism and Buddhism. Shintoism has this belief that encourages a full-body cleansing through water, which is a part of the Misogi ritual. On the other hand, Buddhism introduced the Unjitsu sutra, where it states that to bathe in hot water gains the person seven blessings and seven ailments. Both of these practices advocate the purification of the body and soul. This somehow partly connects to some of the beliefs today, where the Japanese locals would say that continuous bathing at the onsen would cure all physical pain and aches away.
Around the early centuries, Europeans set foot in Japan. It was during this time that the locals would call them “the barbarians." This because the onsen did not appear appealing to the foreigners, who refused to bathe in the hot spring waters. However, the Europeans did have their reasons why they did not want to soak in onsens. They had their belief that hot springs would open up the pores of the skin, inviting diseases to live in their bodies. Over time, these heated baths proved the Europeans wrong as the waters contain healing properties that help with joint pains, blood pressure, and fatigue. It has also been proven that its waters improve blood circulation and body detoxification, helping with weight loss and skin rejuvenation. Men and women also bathed together back in the early days but had to stop the practice when the Japanese opened their doors to the Western people.


Notable Onsens

The oldest onsen recorded in the country is the Dogo Onsen, a bathhouse located on the island of Shikoku. In historical tales, emperors and deities would visit the onsen themselves. In popular culture, the onsen gained another age of fame when it inspired the bathhouse where Chihiro works in the award-winning animated movie “Spirited Away” by Studio Ghibli. Established in 705 AD is another recognized onsen worldwide, which is Nishiyama Onsen Keiunkan. The ryokan is a Guinness World Record holder for being the oldest hot spring inn, having a 1300-year history.
Most Famous Onsens in Japan Most Famous Onsens in Japan

Onsen Standards

Though the term “onsen” has become flexible, either referring to natural hot spring baths or a ryokan facility, strict laws and standards have made the onsen definition more concise. First, onsens must have the required level of minerals. Second, hot spring baths must keep their minimum temperature at 25 degrees celsius. Japan also has another law that bans accommodations from referring to themselves as “onsen” if their hot springs do not qualify the required mineral levels. Interestingly, there are companies in Japan that deliver the recommended water minerals to hotels and bathhouses in Kyoto and Tokyo. A stay in a traditional ryokan can equal the cost of a 4-star hotel. Sometimes this is because of the upscale delicacies in dinners, which are made with local ingredients.
In 2018, according to the Japanese Ministry of Environment Data on Hot Springs, it has been recorded that Japan has over a thousand hot springs, having over 27,000 natural sources and 3038 or more onsen towns, respectively. People around the world still plan their travels to Japan to witness its relaxing treatment and healing benefits, taking their onsen experience as their souvenirs. The onsen waters continue to soothe guests, relieving them of aches and pains in their body, and at the same time making skin feel refreshed. It remains the primary factor that attracts both locals and tourists to take a break and unwind.


Onsen Trivia

  • During the 17th century, a doctor had a theory that diseases invade when energy flow in the body gets disturbed or blocked. He resulted in heated hot spring waters with high temperature to have the flow in the body adjusted. Reportedly, his experiment was in Hyogo at the Kinosaki Onsen.
  • Japanese onsens gush about more than 2.6 million liters of water every minute, having half of it a temperature of 42 degrees celsius.
  • According to Japanese history, a samurai would often go to onsens to have their battle wounds treated.
  • “Onsen Musume”, a multimedia project in Japan, is for anime and manga artists to share their onsen characters and have them featured in animation work like video games. The goal of the project is to increase hot spring tourism.
  • According to Japanese legend, animals bathed in the onsens to have their wounds healed.
  • “Toji” is a Japanese word that refers to the therapy onsen gives or its healing capabilities.
  • Accommodations like ryokans and resorts can feature different facilities. Odaiba Oedo Onsen Monogatari is an onsen example that offers a form of foot spa, where their fishes named “doctor fish”, do therapy. Visitors can dip their feet while the “garra rupa” fishes will nibble on them.
  • The waters of the Tamagawa Onsen is claimed to cure light types of cancer. The onsen is also a recommendation for joint pains and arthritis.
  • Radium Onsen Kasumiso is an onsen visited by people for dermatitis treatment.
  • Tokugawa Ieyasu, a famous samurai warrior, trusted that a week spent in an onsen cures all physical pain. He spent a week in Atami Onsen after being a shogun.
  • There are onsens where men and women can use hot springs together.
  • A special type of onsen in Japan known as the Yunessun Hot Spring is a bath filled with red wine.
  • Another special type of onsen is the Jigokudani Monkey Park, where monkeys bathe in the hot spring during the winter season.
Onsen Manners & Etiquette Onsen Tips & How to

What to Do After an Onsen Bath

After unwinding and relaxing, it is also important to note the following steps after bathing. This is to give a proper farewell to the hot spring bath, as well as spreading awareness of follow-up care for the health of the one who bathed.
Rest Before Showering. After dipping and relaxing in an onsen bath, one should not quickly spring up from the tub or bath area and proceed with a post-washing routine. This is because it weakens the treatment and effects one has gotten from the onsen.
Opt for a Cold Shower. One should take a cold shower rather than a warm or hot one after taking a hot bath cool down. Bathers can dry themselves by patting their towels on their skin and hair.
Post-Shower Necessities. Some bathhouses require people to bring their shampoos, soaps and hair conditioners, but other onsens provide these in their changing rooms. Guests can use hair dryers and combs after taking a shower.
Onsen Eggs. An onsen delicacy that is must-try after a hot spring bath is the “onsen egg” or the “onsen tamago”. The name literally means “hot spring eggs” in the Japanese language. It is a slow-cooked egg from the water heat of the onsen itself and its steam. Sometimes travelers would stop by hot springs to have their own onsen tamago, while other onsen towns would have stalls that sell this specialty. In the Owakudani Valley of Hakone, eggs would turn black due to the chemicals from the water.
After-Shower Beverages. A must-try for guests after dipping is the drinking of milk. This is usually sold in bathhouses and other onsen areas. Recommended beverages are coffee milk and fruit milk, which are favorites of long-time bathers. One can also opt for water just to help the inside of their bodies adjust to the normal temperature.
Take Another Break. Other guests can explore the ryokan or see nearby attractions after soaking in the rejuvenating waters. However, if one wants an extended moment of relaxation, accommodations like hotels and inns welcome guests to try out their massage chairs and couches.
Do Not Over-bathe. It is tempting to take a relaxing dip all over again after a satisfying relaxation from the hot spring bath. However, even though it depends on the person, one’s skin can only take so much, considering there are properties like acid and other elements in the onsen waters. Give the body a rest and opt for a massage instead.
Onsen Manners & Etiquette

Hot Spring Types

Aside from being known as the miracle water, onsens also have a lot to offer. Depending on the respective types of waters, these natural treatments vary from their source. These water sources provide "bathers," not just relaxation but also safe and beneficial health packages that range from external necessities to beauty advantages.
Acidic Spring. Onsens usually have acidic content, which is beneficial for the skin. However, not all can tolerate their properties. Also known as “sansei sen”, this hot spring is recommended for people with sensitive skin. Acidic spring claims to have healing properties for people who struggle with rheumatism and skin disease. It is also a recommendation for people who wish to have tighter skin.
Aluminum Spring. Cancer aluminum or “ganaruminiumusen” is known for its acidic benefits that help a lot in cleansing. It is also effective in treating chronic skin diseases like rashes and athlete’s foot. It is also said to be bitter though people should not try to drink while bathing in the hot spring.
Carbonated Spring. A carbonated characteristic is not only associated with soft drinks or sodas, but also with onsens. This type of water can help people with blood circulation and body detoxification. Just like how carbon tickles the tongue and mouth, the same characteristic will be felt while bathing in this spring.
Chloride Spring. Chloride spring is salt-based water that possesses healing properties beneficial to burns, cuts, and other scratches a skin might have. It also comes in varieties namely calcium, magnesium, and salt. Aside from healing, it helps with hydration and is known to have a salty taste, though it is not advisable to drink the waters while bathing.
Copper-Iron Spring. Usually, onsens display clear or blue steamy waters, but what makes this spring distinct is the yellow appearance due to metal properties that come in contact with air. Sometimes Copper-Iron springs also appear red due to the oxidation. It is known to help those who struggle with hypertension and menstrual disorders.
Ferruginous Spring. Ferruginous Springs can come as carbonated iron waters or melanterite. The spring appears brown, which is due to the high iron content. Its water properties are helpful for people who suffer from menstrual disorders and anemia
Radioactive Spring. This spring can also be referred to as “hosanosen”. It is a hot spring known for having special water content. It is most beneficial for those who have issues with high blood pressure, rheumatism, and gout.
Simple Spring. Known as the “Simple Hot Spring” or “Simple Thermal Spring”, this type of water is usually seen in onsen facilities, displaying a transparent appearance. The spring is ideal for sensitive skin as it is more gentle compared to other acidic hot springs. The water is odorless and has no taste, though it is not advisable to drink from any onsen facility. It also possesses strong alkaline content that helps in insomnia and depression, as it is known to soothe and calm the one who bathes in its waters.
Sodium Bicarbonate Saline Spring. Also referred to as “tansan suisi ensen”, this type of spring is known to make the skin smooth. It is dubbed as the spring that possesses water that makes skin beautiful. Interesting to note is that people who love this type of spring involve it in their skincare, usually in the form of a facial mask.
Sulfate Spring. It is known that hot springs can cure aches and tension, but what is more interesting is that it also stretches its curing abilities in external damages like cuts, bruises, and scratches. The sulfate spring comes in three types namely calcium, magnesium, and sodium, which is beneficial for those who suffer from constipation. Its waters are soothing for the skin, where it acts as a prep ingredient in skincare, just like a toner, when in the beauty world.
Sulfur Spring. When people smell sulfur, it often reminds them of rotten eggs. With its smell, other people might be skeptical about trying this type of bath. Fret not as it comes with healing benefits and effects that massage high blood pressure and diabetes away. It is also a natural treatment for blemishes, rashes, and acne, helping people achieve a clear complexion or improvement in appearance.


Bath Types

It is often heard how hot springs can be enjoyed indoors or outdoors, both privately or publicly. It is also true how one can have the option to bathe separately, but how does one differentiate a sento from a rotenburo? Is heated tap water still considered an onsen? Here is a guide to give readers an idea of the types of baths and what they might want to try next.

Onsen. The onsen is commonly known as the beloved “hot spring". It has water elements ranging from iron, sulfur, and sodium chloride, just to name a few. During traditional times, onsens were outdoor baths with waters coming from natural hot spring resources. Over time, it has evolved to bathhouses and ryokan facilities and is now referred to as hot water springs heated by either volcanic or non-volcanic sources. It is celebrated by bathers either out in the open-air or exclusive areas. Sometimes an onsen can be a combination of both, being a semi-open-air bath.
Ashiyu.  An “ashiyu” is a type of public bath dedicated to the feet. The term is a combination of the Japanese character alphabets “ashi”, meaning foot, and “yu”, which means hot water. Ashiyus are situated near onsens or around a town, specifically corners. Sometimes an ashiyu also sits near stations and parks. Foot baths are usually free, but some areas require a certain fee. This type of bath is a good help for muscle tensions, stress, and the immune system.
Daiyokujo. Daiyokujo is a word that means “large bathing area". It is found in accommodations like hotels and traditional Japanese inns. At times, it also takes the form of an onsen, though sometimes it is also not considered as a hot spring bath.
Kashikiriburo. Kashikiriburo is another type of bath mostly enjoyed by families, couples, and sometimes tattoo-wearers. The word “kashikiri” means “reservation” when translated from Japanese. This makes the kashikiriburo a rental onsen reserved for private and exclusive use. These types are in hotels, resorts, and traditional accommodations.
Mizuburo. Hot spring baths are beloved all around Japan, but so are the “mizuburos,” also known as the “cold water bath”. These are usually situated near saunas, with the purpose to help cool down those who had just a relaxing moment. It is separated from the main bath when in a hot spring facility.
Rotenburo. Also referred to as “notenburo”, is one of the most sought-after baths. It is a combination of Japanese characters “Ro” meaning having no surrounding wall, and “ten” meaning sky. This type is an outdoor bath either placed in a garden or up on a high location overlooking lakes, oceans, mountain views, and other natural surroundings.
Sento. Back in the Nara Period, “sento” baths were in places where priests, who practice Buddhism, used them in rituals for cleansing. Today, these baths are in traditional Japanese inns or communal bathhouses, where people bathe in it, provided they pay an entrance fee. Its waters do not come from hot spring resources, but bathhouses usually heat tap waters instead. It is more common in cities of Japan and is also well-loved by the bathers.
Super Sento. Super sentos are public bathhouses that have bigger areas for bathing. They also display a variety of facilities ranging from massage treatments to restaurants. This type of bath can also appear to be a resort-like place.
Teyu Bath. This type of bath is an onsen specifically for the hands. A teyu is a hand bath that can be used by groups. A teyu bath is also enjoyable during an ashiyu or a footbath. Ashiyus and teyus are ideal during the winter season.
Uchiyu. An uchiyu is similar to the sento, where baths are enjoyed by people indoors. The difference is that the waters used in this bath are from natural hot springs, and bathers have the option to enjoy serene moments in a closed area. It usually appears as a tub inside buildings like traditional Japanese inns and hotels.
Utaseyu. Utaseyu is a hot spring bath known as “the waterfall bath” or “the beating water”. Its waters come from a higher setting, falling on the person who bathes. It is beneficial for the shoulders, neck, and lower back. The person can sit, stand, or sometimes even lay down and adjust the body placement so that the water pressure can hit the point where their body needs pressure. Just be sure not to take too long for a body part to get hit by water, for it can cause or worsen the pain.


  • Wide & Mackintosh, (2018) Onsen of Japan: Japan's Best Hot Springs and Bathhouses
  • Serbulea, M., & Payyappallimana, U. (2012). Onsen (hot springs) in Japan—Transforming terrain into healing landscapes.
  • Stober, I., & Bucher, K. (2013). History of geothermal energy use.


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Onsen Manners and Etiquette