Carbon Dioxide Springs: "The Bubble Waters" for Gentle Circulation

Saga Yamato Onsen Amandi

佐賀県 Yamato, Saga City

What is a Carbon Dioxide Spring?

A carbon dioxide spring contains free carbon dioxide (CO₂) at 1,000 mg per kilogram of spring water or more. These springs are rare in Japan but notable examples exist in Nagano and Oita prefectures.

When you bathe, tiny CO₂ bubbles cling to your skin — nicknamed "the bubble waters" or "ramune waters." The CO₂ absorbed through the skin dilates peripheral capillaries, so even lukewarm water (35–38°C) warms the body effectively with less burden on the heart than hot springs.

Indications for Bathing

• CutsThe enhanced blood flow from absorbed carbon dioxide may help support the body's natural healing process for minor wounds. This improved circulation can deliver more oxygen and nutrients to the skin's surface.
• Peripheral circulatory failureCarbon dioxide absorbed through the skin directly expands peripheral capillaries, increasing blood flow to the body's extremities. This effect is the primary benefit of these springs for improving poor circulation.
• Excessive sensitivity to coldEven in lukewarm water, the vasodilation caused by CO₂ provides a deep warming effect that boosts circulation. This unique “chemical warming” can relieve persistent coldness without putting stress on the heart.
• Autonomic instabilitySoaking slowly in the characteristically lukewarm water helps shift the body towards a state of rest, making the parasympathetic nervous system dominant. This process can help regulate and stabilize an imbalanced autonomic nervous system.

Indications for Drinking

• Gastrointestinal hypofunctionWhen consumed, the carbon dioxide in the spring water can provide gentle stimulation to the stomach's mucous membranes. This action may help promote gastric motility and the secretion of digestive juices, which can be beneficial for sluggish digestive function.

How to Bathe in a Carbon Dioxide Spring

1. CO₂ escapes at high temperatures — soak in a lukewarm source (35–38°C) for longer, do not stir the water.The therapeutic benefits of these springs come from the dissolved carbon dioxide gas, which escapes at higher temperatures. Soaking in lukewarm water (around 35–38°C) is most effective, as it allows the gas to remain in the water for longer. Avoid stirring the water to keep the CO₂ from dissipating.
2. Gently lower yourself into the water; agitation disperses the bubbles.The small bubbles that cling to your skin are the source of the spring's unique effects. To preserve these carbon dioxide bubbles, you should enter the bath slowly and move gently. Vigorous movement can agitate the water, causing the beneficial gas to disperse into the air.
3. Well-suited for the elderly and those with heart conditions — stay hydrated.By dilating blood vessels, these springs warm the body effectively even at lower temperatures, which reduces the strain on the heart compared to hotter baths. This makes them a good option for older bathers or those with certain health concerns. As with any onsen, remember to drink water to stay hydrated.