Onsen In & Around Nagano
The Many Benefits of Onsen

The Many Benefits of Onsen

Many cultures have long recognised the health benefits of soaking in hot and mineral springs. From the Romans and their famous baths, to present-day Scandinavia and many other examples, people have been seeking-out natural hot and mineral springs for as long as we have records.

Perhaps more than any other country, Japan has always acknowledged the many – some known and some presumed – benefits of regularly making use of its many naturally-occurring hot springs. Originally used for medicinal purposes, many people now visit onsen purely for relaxation with the curative properties of specific hot springs also still attracting many visitors.


The health benefits of onsen


‘Balneotherapy’ is the study of the health benefits of bathing in natural hot springs and mineral spas. Proponents of this study investigate the use of both hot and cold water, along with massage, relaxation and stimulation using water, and the benefits of mineral rich spas including silica, sulfur, radium and other properties.

In theory, these minerals and other elements penetrate the body, promoting hormone secretion. When you enter an onsen, the sympathetic nerve becomes predominant, blood pressure rises, heart rate goes up and blood sugar increases. To counter-act this, the parasympathetic nerve is activated and in restoring equilibrium to the body, it is claimed to have a restorative and curative effect.

Japanese have long sought-out hot springs for this reason. There are many types of water with specific (claimed) benefits including:


–  tanzyun-sen (simple water): the most common type of onsen, the water has a balanced mineral content with no predominant element, colour or odour. Many onsen fall under this classification and as such, there is a huge diversity in their exact properties and benefits. Simple water is well-suited to all ages, from young to old. Gero Onsen is known for its tanzyun-sen.


–  sansei-sen (acidic water): has a strong bacterial effect and often used for skin treatment including healing scars and chronic skin conditions. Acidic water results from a mixture of volcanic gas and ground water and is said to remove old skin. However some people find he affect too strong and it’s a good idea to wash-off the water after bathing. Whatever you do, do not drink it. Kusatsu Onsen is one of Japan’s most renowned towns for sansei-sen.


–  bijin-no-yu (alkaline water): known as the ‘onsen of beautiful ladies’, alkaline water feels thick and silky. It exfoliates the skin, making it smooth and removing spots, hence its association with beauty and anti-ageing. Hirugami Onsen is famous for its bijin-no-yu.


–  iou-sen (sulfuric water): often carries a strong sulfuric smell and colour in the water making it easy to identify. The gas clears the throat and counteracts ailments including bronchitis. The water is said to open blood vessels and therefore helps protect against heart disease, arteriosclerosis and other skin diseases. The milky white water of Manza Onsen is one of Japan’s best destinations to try iou-sen.


–  gantetsu-sen (iron water): is clear in colour but changes to red/brown once exposed to oxygen and the iron is oxidized. It is easy to recognise as there is a smell of rust and a bitter, metallic taste. The iron content means the water treats anemia and menopausal or menstruation disorders. These positive affects for women mean that it is also referred to as ‘fujin-no-yu’ or ‘water of women’. Said to also aid circulation and blood health, the water is often drunk in small amounts. Visitors to Shibu Onsen can try gantetsu-sen – both soaking and drinking it (pictured below).


–  tansan-sen (carbonated water): looks like normal water but small bubbles stick to your skin. Said to improve circulation quicker than normal water and is good for detoxing. Tansen-sen is rare and hard to find.

For recommendations as to where to find some the region’s best onsens, including those listed above, please refer to our ‘Visit the Best Onsen Towns in Central Japan‘ page.


Finally, a world about ‘Hot Water Flowers’


In some onsen you might notice particles floating in the water. Often white and fluffy, this can be off-putting the first time you encounter it as people understandably assume the water is not clean. Don’t be alarmed. What you are experiencing is called ‘yu-no-hana’ or ‘hot water flowers’, naturally occurring sediments floating in the water.

Yu-no-hana come from deep inside the Earth, and float to the surface in the thermal water. They are clean, meant to be there, and if you see a lot of them, the onsen you are enjoying is likely to be famous for them.


Onsen In & Around Nagano

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