An alkaline simple-sulfur spring drawn at 50.9 °C — high-temperature class. The water is near-colorless and clear at the wellhead but carries an unmistakable hydrogen sulfide note, and the 12.4 mg/kg of HS⁻ comfortably clears the sulfur-spring threshold. At pH 8.8 it sits in the alkaline band, soft on the skin in the classic Bessho beauty-water style.
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
Aches & joints
Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.
stiff shoulders
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⁺79.6mgP25 national85%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺12.1mgP29 national15%
- PotassiumK⁺0.70mgP9 national0.5%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻90.8mgP53 national44%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻40.2mgP25 national27%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻33.1mgP19 national13%
- Hydrogen sulfidesulfur character — antibacterialHS⁻12.4mgP96 national9%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻8.1mgP45 national6%
- Fluoridetrace; drinking limits applyF⁻0.90mgP45 national1%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃48.9mgP28 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂2.0mgP19 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.20mgP68 national
- ArsenicAs< —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.
- Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
- Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
- 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