When you hear the word "Onsen," what do you imagine? A steaming open-air bath, a hidden hot spring surrounded by snow, or a hot spring town where people stroll in yukata? Many foreign travelers visiting Japan look forward to the onsen experience as a highlight of their trip.
But what exactly is an "onsen"? How is it different from a regular bath? This article provides a comprehensive explanation for those experiencing Japanese onsen for the first time, covering everything from the definition of onsen to its culture and how to enjoy it.
Definition of Onsen: Defined by Law
Definition According to Japan's Onsen Law
In Japan, onsen is clearly defined by a law called the "Onsen Law." Onsen is:
"Hot water, mineral water, and steam or other gases (excluding natural gas with hydrocarbons as the main component) that meet one of the following conditions, gushing from the ground"
Condition 1: Temperature of 25°C or higher The water temperature must be 25°C or higher at the point it gushes from the ground.
Condition 2: Contains a certain amount of specific components It must contain one or more of the 19 specified components, such as lithium ions, hydrogen ions, iodide ions, iron ions, in a prescribed amount or more.
Important Points
In other words, it doesn't necessarily have to be "hot." There are onsen with a temperature of 25°C (called cold mineral springs). Conversely, if it contains specific components, it can be certified as an "onsen" even if the temperature is low.
Onsen Analysis Certificate
Every onsen facility displays an "onsen analysis certificate." This is an official certificate that lists the components, temperature, pH value, etc., of the onsen. Be sure to check it when you visit an onsen facility.
Why Japan is a Hot Spring Superpower
Geological Features of Volcanic Japan
The Japanese archipelago is located on the Ring of Fire. This geological feature makes Japan one of the world's leading hot spring superpowers.
Statistics on Japan's Onsen
- Number of Hot Spring Sources: Over 27,000
- Number of Hot Spring Areas: About 3,000
- Number of Onsen Facilities: About 18,000
- Annual Users: Approximately 130 million people
All 47 Prefectures Have Onsen
From Hokkaido to Okinawa, every prefecture in Japan has onsen. This is extremely rare worldwide.
Abundance of Onsen Resources
Japanese onsen are not only abundant in quantity but also in quality. All 10 types of spring qualities exist, allowing you to enjoy onsen with various benefits.
Differences Between Onsen and Regular Baths
1. Natural Underground Water
Onsen is natural underground water that gushes from deep underground. It is not heated tap water like a regular bath.
2. Rich in Mineral Components
Onsen contains various mineral components. These components create the unique benefits of onsen.
3. Temperature and Flow Rate
Many onsen naturally gush at an optimal temperature (38-42°C). Also, new onsen water is constantly flowing.
4. Color, Scent, Texture
Depending on the spring quality, onsen can have various colors, scents, and textures. Milky white, green, brown. The scent of sulfur. A silky texture. These are characteristics unique to natural onsen.
What is Gensen Kakenagashi?
Definition of Gensen Kakenagashi
"Gensen Kakenagashi" is a method where freshly gushed onsen water is continuously poured into the bath, and the overflow is discharged.
Benefits of Gensen Kakenagashi
- Fresh: Always new onsen water is poured
- Rich in Components: Minimal dilution or heating
- Hygienic: Clean as it is not recirculated
- High Efficacy: Experience the original benefits of onsen to the fullest
Difference from Circulation System
The circulation system filters and sterilizes used onsen water for reuse. While excellent in terms of hygiene, the onsen components are diluted.
How to Identify
Onsen facilities display signs like "Gensen Kakenagashi" or "100% Source." The "Source Usage Status" is also listed on the onsen analysis certificate.
Differences Between Onsen and Sento
Onsen
- Uses natural onsen
- Contains components defined by the Onsen Law
- Mostly located in suburbs or tourist areas
- Bathing fee is around 500-2,000 yen
Sento
- Bath heated with tap water
- Community-based public bath
- Located in residential areas of cities
- Bathing fee is around 450-500 yen (in Tokyo)
Onsen Sento
However, there are "onsen sento" where natural onsen springs are available even in sento. These are hidden spots where you can enjoy onsen in urban areas.
History of Japanese Onsen
Ancient Times: From Mythical Ages
The history of Japanese onsen is very old and can be said to be synonymous with Japanese history itself.
Descriptions in Myths
- 'Kojiki' and 'Nihon Shoki': Japan's oldest historical books already mention onsen
- Dogo Onsen: Approximately 3,000 years of history (one of Japan's oldest)
- Arima Onsen: About 1,300 years of history
Heian Period: Nobles' Hot Spring Therapy Culture
During the Heian period (794-1185), onsen was already used as a place for healing. The culture of "toji," where nobles visited hot spring areas to cure illnesses, began.
Edo Period: Commoners' Onsen Culture
In the Edo period (1603-1868), onsen culture spread to the common people.
- Onsen Ranking: A culture of ranking onsen like sumo rankings
- Toji Trips: A custom of staying at hot spring areas for several weeks during the off-farming season
- Development of Onsen Towns: Formation of onsen towns with restaurants and inns
Meiji Period and Beyond: Modernization and Tourism
Since the Meiji period (1868-), onsen has developed not only as a place for medical treatment but also for tourism and leisure.
- Development of Onsen Medicine: Scientific research on the benefits of onsen
- Development of Railways: Improved access from urban areas to onsen areas
- Development of Onsen Inns: Establishment of luxury inn culture
Modern Times: Onsen Boom and Wellness Tourism
Today, onsen is deeply rooted in Japanese life. It is also very popular among foreign tourists and has become a must-experience in Japan travel.
Onsen Spring Qualities: 10 Classifications
Japanese onsen are classified into 10 types based on the components they contain.
1. Simple Springs
- Characteristics: Low in components, mild
- Benefits: Fatigue recovery, health promotion
- Gentle on Skin: Recommended for children and the elderly
2. Chloride Springs
- Characteristics: Contains salt, often near the sea
- Benefits: Warming effect, improvement of cold sensitivity
- Experience: Less likely to catch a chill
3. Bicarbonate Springs
- Characteristics: Known as "beauty bath"
- Benefits: Skin beautification, smooth skin
- Color: Transparent or milky white
4. Sulfate Springs
- Characteristics: Bitter taste
- Benefits: Promotes blood circulation, fatigue recovery
- Experience: Warms easily
5. Carbon Dioxide Springs
- Characteristics: Contains carbon dioxide gas
- Benefits: Promotes blood circulation, "heart bath"
- Experience: Bubbles attach to the body
6. Iron Springs
- Characteristics: Contains iron
- Benefits: Improves anemia
- Color: Brown (oxidizes when exposed to air)
7. Sulfur Springs
- Characteristics: Sulfur scent
- Benefits: Skin diseases, skin beautification
- Color: Milky white or transparent
8. Acidic Springs
- Characteristics: Low pH value (acidic)
- Benefits: Antibacterial effect, skin diseases
- Example: Kusatsu Onsen (pH 2.1)
9. Radioactive Springs
- Characteristics: Contains radon
- Benefits: Gout, neuralgia
- Caution: Safe in trace amounts
10. Iodine Springs
- Characteristics: Contains iodine
- Benefits: High blood pressure, arteriosclerosis
- Distribution: Relatively rare
Benefits of Onsen: Why It's Good for the Body
Three Effects of Onsen
1. Thermal Effect Soaking in warm water promotes blood circulation and activates metabolism.
2. Water Pressure Effect Water pressure improves the flow of blood and lymph. It also strengthens respiratory muscles.
3. Component Effect Mineral components in onsen are absorbed through the skin or inhaled into the body.
General Benefits
- Fatigue recovery
- Stress relief
- Promotes blood circulation
- Alleviates muscle and joint pain
- Improves cold sensitivity
- Skin beautification
- Boosts immunity
How to Bathe in Onsen: Basic Manners
Before Bathing
- Undress in the changing room
- Carry two towels (a small towel and a large bath towel)
- Store valuables in a locker
Once in the Bathing Area
- Wash your body first (not just rinsing, but with soap)
- Tie up your hair (with a rubber band or clip)
- Do not put towels in the bath (place them on your head)
While Bathing
- Enter quietly (do not jump in)
- Do not stay too long (5-10 minutes is a guideline)
- Bathe in multiple sessions
After Bathing
- Lightly wipe your body (to leave onsen components)
- Rehydrate (be sure to drink water)
- Rest (for about 30 minutes)
Diversity of Onsen Culture
Mixed Bathing Culture
Mixed bathing was once common in Japan, but now most are gender-separated. Some traditional onsen areas still have mixed baths.
Family Baths
"Family baths" are available for families with small children or couples to use privately.
Foot Baths
"Foot baths" allow you to soak only your feet in onsen while keeping your clothes on. They can be easily enjoyed while strolling through onsen towns.
Drinking Onsen Water
At some onsen, you can drink the onsen water (only at onsen where drinking is allowed).
Conclusion: Onsen is the Core of Japanese Culture
Onsen is not just a bathing facility. It is a mirror reflecting Japan's history, nature, culture, and the lifestyle of the Japanese people.
The abundant onsen resources are a blessing of volcanic Japan. The hot spring therapy culture that has continued for over 1,000 years. The Japanese aesthetic that values harmony with nature. The unique communication culture of "naked companionship" that arises from bathing together naked.
All these elements combine to form the unique Japanese onsen culture that is unlike any other in the world.
When you visit Japan, be sure to experience onsen. It is not just a tourist activity, but a special experience that touches the essence of Japanese culture.
Onsen is the heart of Japan.
