A sodium-calcium chloride spring carrying sulfur, salty and heat-retaining in character. At the wellhead its pH of 10.0 makes it strongly alkaline, giving the pronounced slippery feel of Japan's beauty-water family. It carries hydrogen sulfide, so a faint rotten-egg note and a light salty tang come through at the source. A cold-mineral-leaning low-temperature spring (33 C at source), it is reheated for bathing.
Good for
Skin conditions
Sulfur and acidic waters are antibacterial and keratolytic, studied for atopic dermatitis and psoriasis.
atopic skin, eczema
Circulation
Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.
tired legs
Warming
Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, netto 熱の湯).
cold sensitivity
Smooth skin
Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.
dry, rough skin
Cuts
Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.
minor wounds
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
Sensitive-skin caution
Strongly acidic or sulfur-rich water can sting broken, atopic-flare, or dry elderly skin. Ease in slowly and rinse off if it stings.
broken or dry skin
- see attached panel
Full composition
The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺425mgP73 national79%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺97.9mgP73 national21%
- PotassiumK⁺2.7mgP25 national0.3%
- AmmoniumNH₄⁺0.10mgP23 national0.2%
- MagnesiumMg²⁺0.10mgP11 national0.0%
- BariumBa²⁺0.10mgP50 national0.0%
- StrontiumSr²⁺0.10mgP24 national0.0%
- AluminumAl³⁺0.0000mg0.0%
- Iron (II)Fe²⁺0.0000mg0.0%
- Iron (III)Fe³⁺0.0000mg0.0%
- HydrogenH⁺0.0000mg0.0%
- LithiumLi⁺0.0000mg0.0%
- ManganeseMn²⁺0.0000mg0.0%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻775mgP80 national93%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻18.6mgP63 national3%
- HSiO3HSiO₃⁻41.1mgP86 national2%
- SulfateSO₄²⁻6.7mgP17 national0.6%
- Hydrogen sulfideHS⁻4.3mgP87 national0.6%
- BO2BO₂⁻4.8mgP76 national0.5%
- FluorideF⁻1.8mgP57 national0.4%
- HydroxideOH⁻1.6mgP91 national0.4%
- BromideBr⁻2.5mgP75 national0.1%
- BicarbonateHCO₃⁻60.0mgP34 national0.0%
- IodideI⁻0.30mgP61 national0.0%
- ThiosulfateS₂O₃²⁻0.10mgP43 national0.0%
- Hydrogen phosphateHPO₄²⁻0.0000mg0.0%
- HSO4HSO40.0000mg0.0%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃0.0000mg
- Phosphoric acidH₃PO₄0.0000mg
- Metaarsenious acidHAsO₂0.0000mg
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂0.0000mg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂0.0000mg
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.0000mg
- ArsenicAs< —mg
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
- see attached panel
Evidence
- Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
- Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
- Tei C, Kihara T. Waon Therapy for Chronic Heart Failure. J. Cardiology 53(2):214–218, 2009.
- Coavoy-Sánchez SA et al. Hydrogen sulfide and dermatological diseases. Int. J. Dermatology, 2019.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- Akiyama H et al. Antimicrobial effects of acidic hot-spring water on S. aureus. J. Dermatological Science 24(3):193–200, 2000.
- Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
- Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.
- Ministry of the Environment, Japan. 禁忌症及び入浴又は飲用上の注意事項 (2014 notice).official