湯泉地温泉1号・2号混合源泉Tosenji Onsen #1 and #2 Mixed Source
A naturally sulfur-bearing simple thermal source, blending the village's #1 and #2 wells in Totsukawa. Alkaline (pH 8.9) and hypotonic, with a soft, slippery feel and a recognizable faint sulfur note at the wellhead. Lightly mineralized — total dissolved solids just 236 mg/kg — yet free sulfide species (HS) reach about 5 mg/kg, enough to qualify as a true sulfur spring under the Japanese classification.
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
- 急性疾患（特に熱のある場合）
- Active tuberculosis
- Malignant tumor
- 重い心臓病
- 呼吸不全
- Renal failure
- Bleeding disorders
- Severe anemia
- その他一般に病勢進行中の疾病
- 妊娠中（特に初期と末期）
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⁻5.9mgP8 national5%
- Hydrogen sulfidesulfur character — antibacterialHS⁻5.0mgP91 national5%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻5.9mgP17 national4%
- NitrateNO₃⁻0.06mgP21 national0.1%
- Bromidetrace, sea-originBr⁻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 antibacterialHBO₂0.0000mg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂0.20mgP13 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.0000mg
- ArsenicAsNDmg
- CadmiumCdNDmg
- CopperCuNDmg
- Mercurytoxic trace — part of the drinking-safety checkHgNDmg
- LeadPbNDmg
Measured at the source
On the certificate
- Chronic digestive disorders
- Cold sensitivity
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