十津川温泉2号・7号混合源泉Totsukawa Onsen Wells No.2 + No.7 Mixed Source
A bicarbonate spring led by sodium with a chloride layer, blended from Totsukawa wells No.2 and No.7. Hot at 58 °C and weakly alkaline, it carries the soft, skin-smoothing feel of a soda-style water with a salty edge that helps the heat linger after the bath.
Good for
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
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
Warming
Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, nettō 熱の湯).
cold sensitivity
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
- 病気の活動期(特に熱のあるもの)、活動性の結核、進行した悪性腫瘍又は高度の貧血など身体衰弱の著しい場合、少し動くと息苦しくなるような重い心臓又は肺の病気、むくみのあるような重い腎臓の病気、消化管出血、目に見える出血があるとき、慢性の病気の急性増悪期
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⁺440mgP73 national91%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺17.4mgP36 national4%
- Potassiumminor; matters for drinking limitsK⁺22.2mgP66 national3%
- LithiumLi⁺1.4mgP86 national0.8%
- MagnesiumMg²⁺2.0mgP35 national0.7%
- AmmoniumNH₄⁺1.8mgP79 national0.5%
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺0.89mgP60 national
- Manganesetrace; companion to iron springsMn²⁺0.03mgP19 national
- Aluminumshows up in acidic volcanic waterAl³⁺0.02mgP22 national
- ZincZn²⁺0.01mgP43 national
- BariumBa²⁺0.01mgP30 national
- StrontiumSr²⁺NDmg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻931mgP89 national63%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻293mgP63 national34%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻9.6mgP50 national1%
- FluorideF⁻1.8mgP56 national0.4%
- SulfateSO₄²⁻3.1mgP12 national0.3%
- Hydrogen sulfideHS⁻0.48mgP53 national0.1%
- Bromidetrace, sea-originBr⁻NDmg
- Hydrogen phosphateHPO₄²⁻NDmg
- NitrateNO₃⁻NDmg
- Thiosulfateoxidized sulfurS₂O₃²⁻NDmg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃89.8mgP52 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂2.5mgP23 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂26.0mgP56 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.46mgP71 national
- ArsenicAsNDmg
- CadmiumCdNDmg
- LeadPbNDmg
Measured at the source
On the certificate
- 筋肉又は関節の慢性的な痛み又はこわばり(関節リウマチ、変形性関節症、腰痛症、神経痛、五十肩、打撲、捻挫などの慢性期)
- 運動麻痺における筋強直
- 冷え性、末梢循環障害、胃腸機能の低下、軽症高血圧、耐糖能異常(糖尿病)、軽い高コレステロール血症、軽い喘息又は肺気腫、痔の痛み、自律神経不安定症、ストレスによる諸症状(睡眠障害、うつ状態など)、病後回復期、疲労回復、健康増進
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.
- Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- 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.