Carbon dioxide hot springs are a rare type of onsen in Japan where fine bubbles adhere to the skin upon bathing. Also affectionately known as 'Ramune Bath' or 'Bubble Bath', these springs are a must-visit if you find one, as they are only available in limited locations in Japan.

What is a Carbon Dioxide Hot Spring?

A carbon dioxide hot spring refers to an onsen that contains a certain amount of free carbon dioxide. If the onsen water contains more than 1,000 mg of free carbon dioxide per kilogram, it is classified as a carbon dioxide hot spring.

Also known as 'carbonated springs', these are hot springs where carbon dioxide, similar to the carbonation in soft drinks, is dissolved.

Appearance and Characteristics

Color: Transparent Smell: Almost odorless Texture: Fizzy sensation Temperature: Often lukewarm (30-40°C)

The most notable feature is the fine bubbles that adhere to the skin when bathing. These bubbles are actually carbon dioxide gas.

Why Do Bubbles Form?

The carbon dioxide dissolved in the hot spring water vaporizes due to body temperature, and these bubbles then adhere to the skin.

It's the same principle as bubbles rising in a glass of champagne. Seeing your entire body covered in fine bubbles is quite fascinating.

Why is it Called 'Heart Bath'?

When you enter a carbon dioxide hot spring, the carbon dioxide gas is absorbed through the skin, causing blood vessels to dilate. This improves blood circulation.

Moreover, since the temperature is often lukewarm (around 30-40°C), it promotes blood circulation without putting a strain on the heart, hence the name 'Heart Bath'.

High-temperature hot springs can strain the heart, but carbon dioxide hot springs warm the body even at lukewarm temperatures, making them ideal for those concerned about heart health.

Mechanism of Blood Circulation Promotion

The carbon dioxide absorbed through the skin dilates blood vessels. When blood vessels dilate, blood flow increases. As blood flow increases, the body warms up.

You can experience the mysterious sensation of your body warming up even at lukewarm temperatures. This is the charm of carbon dioxide hot springs.

Why Are They Rare in Japan?

Carbon dioxide hot springs are a very rare type of spring in Japan.

For carbon dioxide to dissolve in hot springs, special geological conditions are necessary. There must be an abundance of volcanic gas and low temperatures. Such conditions are rare in Japan.

While Europe has many carbon dioxide hot springs, in Japan, they are only found in limited places like Nagayu Onsen in Oita Prefecture.

Main Benefits

General indications for carbon dioxide hot springs:

• High blood pressure
• Arteriosclerosis
• Heart disease
• Cold sensitivity, peripheral circulation disorders
• Chronic skin diseases
• Cuts, burns

They are said to be effective for heart and vascular diseases.

Representative Carbon Dioxide Hot Springs

Nagayu Onsen (Oita Prefecture): A representative carbonated spring in Japan, containing a high concentration of carbon dioxide.

Arima Onsen's Carbonated Spring Source (Hyogo Prefecture): A carbonated spring where you can also drink the water.

Fukiage Onsen (Kagoshima Prefecture): A natural carbon dioxide hot spring.

Michinoku Onsen (Aomori Prefecture): A rare carbon dioxide hot spring.

Recommended For

People with heart concerns, those with high blood pressure, those who want to experience rare hot springs, and those who want to enjoy the sensation of bubbles. Carbon dioxide hot springs offer a unique experience in Japan.

Tips for Bathing

To enjoy carbon dioxide hot springs, there are some tips.

Stay Still: Moving your body will cause the bubbles to fall off. Staying still allows more bubbles to adhere.

Soak for a Long Time: To benefit from the carbon dioxide effect, soaking for 15-20 minutes is ideal. Since it's lukewarm, you can stay in for a long time.

Observe the Bubbles: Watching the bubbles on your body is also enjoyable. Over time, the bubbles increase.

Difference from Artificial Carbonated Springs

Recently, 'artificial carbonated springs' are often seen in super sento (public bathhouses). These are hot springs where carbon dioxide is artificially dissolved.

Even with artificial carbonated springs, you can experience the sensation of bubbles and the blood circulation benefits. However, natural carbon dioxide hot springs are also rich in other minerals, making them more valuable.

Conclusion

Carbon dioxide hot springs are a very rare type of spring in Japan. The experience of having bubbles adhere to your body is something you can't enjoy with other types of springs.

As the name 'Heart Bath' suggests, it promotes blood circulation without straining the heart at lukewarm temperatures. It's an ideal hot spring for those concerned about high blood pressure or heart disease.

Carbon dioxide hot springs are only found in limited locations in Japan. If you find one, make sure to take a dip. Experience the sensation of bubbles and the mysterious feeling of your body warming up even at lukewarm temperatures.