湯泉地温泉1号・2号混合源泉Tosenji Onsen No.1 & No.2 Blended Source
A sodium-led simple sulfur spring rising at 52.7 °C — hot, alkaline (pH 8.9), and faintly carrying the rotten-egg note of H₂S at the source. The slippery alkaline feel puts it in Japan's classic 'beauty-water' family, while 5.0 mg/kg of bisulfide and a bicarbonate-carbonate backbone give it a soft, rounded body — a gentle sulfur spring rather than a sharp one.
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⁺64.0mgP19 national96%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺1.6mgP6 national3%
- PotassiumK⁺1.1mgP14 national1.0%
- AluminumAl³⁺0.04mgP27 national0.1%
- BariumBa²⁺0.10mgP53 national0.1%
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺NDmg
- LithiumLi⁺NDmg
- Magnesiummild; a laxative if you drink itMg²⁺NDmg
- Manganesetrace; companion to iron springsMn²⁺NDmg
- AmmoniumNH₄⁺NDmg
- StrontiumSr²⁺NDmg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻102mgP43 national52%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻24.0mgP75 national25%
- Fluoridetrace; drinking limits applyF⁻5.9mgP81 national10%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻6.1mgP9 national5%
- Hydrogen sulfidesulfur character — antibacterialHS⁻5.0mgP91 national5%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻5.9mgP17 national4%
- NitrateNO₃⁻0.30mgP43 national0.1%
- Bromidetrace, sea-originBr⁻NDmg
- Hydrogen phosphateHPO₄²⁻NDmg
- Iodideyellows in air; helps blood lipidsI⁻NDmg
- Thiosulfateoxidized sulfurS₂O₃²⁻NDmg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃20.0mgP5 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂NDmg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂0.20mgP13 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂SNDmg
- ArsenicAsNDmg
- CadmiumCdNDmg
- CopperCuNDmg
- Mercurytoxic trace — part of the drinking-safety checkHgNDmg
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