Kinugawa Nioson no Yu is an alkaline simple sulfur spring. At the wellhead it reads pH 9.6 — strongly alkaline, with the slippery feel that places it squarely in Japan's beauty-water family. Dissolved solids are light at 280 mg/kg, so the water is gentle rather than assertive, but it carries hydrogen sulfide ion and a weak H₂S note is noticeable at the spout. Metasilicic acid at 52.1 mg/kg leaves a thin silica film that makes skin feel noticeably smoother afterwards.
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⁺83.4mgP25 national
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺3.9mgP13 national
- Potassiumminor; matters for drinking limitsK⁺0.50mgP5 national
- Aluminumshows up in acidic volcanic waterAl³⁺0.0000mg
- BariumBa²⁺0.0000mg
- CopperCu²⁺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
- AmmoniumNH₄⁺0.0000mg
- StrontiumSr²⁺0.0000mg
- ZincZn²⁺0.0000mg
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻56.7mgP42 national
- Carbonatestrongly alkaline; slippery feelCO₃²⁻30.4mgP85 national
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻29.7mgP21 national
- Fluoridetrace; drinking limits applyF⁻11.2mgP93 national
- BO2BO₂⁻8.8mgP90 national
- Hydrogen sulfidesulfur character — antibacterialHS⁻2.7mgP80 national
- HydroxideOH⁻0.70mgP81 national
- Bromidetrace, sea-originBr⁻0.10mgP14 national
- AsO2AsO₂⁻0.0000mg
- H2PO4H₂PO₄⁻0.0000mg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻0.0000mg
- Hydrogen phosphateHPO₄²⁻0.0000mg
- HSiO3HSiO₃⁻0.0000mg
- HSO4HSO40.0000mg
- Iodideyellows in air; helps blood lipidsI⁻0.0000mg
- NitrateNO₃⁻0.0000mg
- SS²⁻0.0000mg
- Thiosulfateoxidized sulfurS₂O₃²⁻0.0000mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃52.1mgP31 national
- H2SO4FreeH2SO4Free0.0000mg
- 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
- 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