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, netto 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
From a certificate analyzed in 2023.
- Active stage of any illness (especially with fever), active tuberculosis, advanced malignant tumor, severe anemia or other marked physical weakness, severe heart or lung disease causing shortness of breath on slight exertion, severe kidney disease with edema, gastrointestinal bleeding, visible bleeding, acute exacerbation of a chronic illness
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⁺440mgP74 national91%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺17.4mgP36 national4%
- Potassiumminor; matters for drinking limitsK⁺22.2mgP66 national3%
- LithiumLi⁺1.4mgP85 national0.8%
- MagnesiumMg²⁺2.0mgP35 national0.7%
- AmmoniumNH₄⁺1.8mgP79 national0.5%
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺0.89mgP61 national
- Manganesetrace; companion to iron springsMn²⁺0.03mgP18 national
- Aluminumshows up in acidic volcanic waterAl³⁺0.02mgP23 national
- ZincZn²⁺0.01mgP41 national
- BariumBa²⁺0.01mgP28 national
- StrontiumSr²⁺NDmg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻931mgP89 national63%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻293mgP64 national34%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻9.6mgP49 national1%
- FluorideF⁻1.8mgP57 national0.4%
- SulfateSO₄²⁻3.1mgP12 national0.3%
- Hydrogen sulfideHS⁻0.48mgP51 national0.1%
- Bromidetrace, sea-originBr⁻NDmg
- Hydrogen phosphateHPO₄²⁻NDmg
- NitrateNO₃⁻NDmg
- Thiosulfateoxidized sulfurS₂O₃²⁻NDmg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃89.8mgP51 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂2.5mgP22 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂26.0mgP55 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.46mgP68 national
- ArsenicAsNDmg
- CadmiumCdNDmg
- LeadPbNDmg
Measured at the source
On the certificate
From a certificate analyzed in 2023.
- Chronic muscle or joint pain or stiffness (the chronic phase of rheumatoid arthritis, osteoarthritis, lower back pain, neuralgia, frozen shoulder, bruises, sprains and the like)
- Muscle rigidity associated with motor paralysis
- Cold sensitivity, peripheral circulation disorders, reduced gastrointestinal function, mild hypertension, impaired glucose tolerance (diabetes), mild hypercholesterolemia, mild asthma or emphysema, hemorrhoid pain, autonomic nervous system instability, stress-related symptoms (sleep disorders, depressed mood), convalescence, fatigue recovery, general health improvement
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.