A strongly alkaline simple sulfur spring. The high pH gives a pronounced slippery feel on the skin, placing it in Japan's beauty-water family, while a faint sulfur note and fine bubbles cling at the source. With only 216.6 mg/kg of dissolved solids it is lightly mineralized and gentle on the body.
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
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⁺57.2mgP16 national97%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺1.3mgP4 national2%
- PotassiumK⁺0.20mgP2 national0.4%
- AluminumAl³⁺0.10mgP54 national0.4%
- BariumBa²⁺0.0000mg
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺0.0000mg
- Iron (III)Fe³⁺0.0000mg
- Hydrogenmakes the water acidic — sharp and bactericidalH⁺0.0000mg
- LithiumLi⁺0.0000mg
- Magnesiummild; a laxative if you drink itMg²⁺0.0000mg
- Manganesetrace; companion to iron springsMn²⁺0.0000mg
- StrontiumSr²⁺0.0000mg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻74.2mgP37 national39%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻18.0mgP63 national19%
- HSiO3HSiO₃⁻38.2mgP78 national16%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻10.6mgP13 national10%
- Fluoridetrace; drinking limits applyF⁻2.6mgP64 national4%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻5.1mgP15 national4%
- BO2BO₂⁻3.2mgP76 national2%
- Hydrogen sulfidesulfur character — antibacterialHS⁻1.1mgP71 national2%
- Bromidetrace, sea-originBr⁻0.0000mg
- HSO4HSO40.0000mg
- Iodideyellows in air; helps blood lipidsI⁻0.0000mg
- Thiosulfateoxidized sulfurS₂O₃²⁻0.0000mg
- 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
- ChromiumCr< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
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