An alkaline simple sulfur spring carrying the faint rotten-egg note of hydrogen sulfide. The pH is strongly alkaline, giving the slippery, soft-on-the-skin feel of Japan's beauty-water family. Lightly mineralized and gentle on the body, it makes for a mild, easy soak rather than a heavy mineral bath.
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
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
- acute illness (especially when feverish)
- active tuberculosis
- severe heart disease
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⁺50.6mgP14 national98%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺0.80mgP2 national2%
- PotassiumK⁺0.30mgP3 national0.4%
- AluminumAl³⁺0.0000mg0.0%
- BariumBa²⁺0.0000mg0.0%
- FeTotalFe0.0000mg0.0%
- HydrogenH⁺0.0000mg0.0%
- LithiumLi⁺0.0000mg0.0%
- MagnesiumMg²⁺0.0000mg0.0%
- ManganeseMn²⁺0.0000mg0.0%
- AmmoniumNH₄⁺0.0000mg0.0%
- StrontiumSr²⁺0.0000mg0.0%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻49.5mgP93 national52%
- HSiO3HSiO₃⁻61.2mgP96 national25%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻13.7mgP9 national7%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻8.1mgP19 national5%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻3.5mgP5 national3%
- HydroxideOH⁻1.6mgP91 national3%
- Hydrogen sulfidesulfur character — antibacterialHS⁻2.7mgP81 national3%
- Fluoridetrace; drinking limits applyF⁻0.80mgP41 national1%
- ThiosulfateS₂O₃²⁻1.3mgP75 national0.7%
- AsO2AsO₂⁻0.0000mg0.0%
- BromideBr⁻0.0000mg0.0%
- H2PO4H₂PO₄⁻0.0000mg0.0%
- Hydrogen phosphateHPO₄²⁻0.0000mg0.0%
- HSO4HSO40.0000mg0.0%
- IodideI⁻0.0000mg0.0%
- NitrateNO₃⁻0.0000mg0.0%
- SS²⁻0.0000mg0.0%
- BO2BO₂⁻0.90mgP53 national
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃0.0000mg
- 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
- ArsenicAsNDmg
- CopperCuNDmg
- Mercurytoxic trace — part of the drinking-safety checkHgNDmg
- LeadPbNDmg
Measured at the source
On the certificate
- chronic muscle or joint pain and stiffness
- sensitivity to cold
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.
- 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