A sodium-calcium chloride spring, neutral in pH and softly mineralized at 7,349 mg/kg of total dissolved solids. The water carries the heat-retaining body characteristic of chloride springs, with a faintly cloudy pale tint at the source and a mild salty-bitter tang paired with a whisper of hydrogen sulfide.
Good for
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
- 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
- Renal failure, liver failure
- 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⁺1,608mgP91 national55%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺1,127mgP96 national44%
- MagnesiumMg²⁺4.9mgP50 national0.3%
- PotassiumK⁺5.4mgP35 national0.1%
- Iron (II)Fe²⁺0.90mgP62 national0.0%
- ManganeseMn²⁺0.50mgP66 national0.0%
- AluminumAl³⁺0.10mgP55 national0.0%
- Iron (III)Fe³⁺< —mg
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻4,049mgP92 national91%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻478mgP87 national8%
- FluorideF⁻11.5mgP93 national0.5%
- IodideI⁻0.10mgP35 national0.0%
- Hydrogen phosphateHPO₄²⁻0.0030mgP20 national
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃36.0mgP18 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂10.1mgP56 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂6.6mgP32 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S< —mg
- ArsenicAs0.0050mgP16 national
Measured at the source
On the certificate
- Muscle or joint stiffness (the chronic phase of rheumatoid arthritis, osteoarthritis, lower back pain, neuralgia, frozen shoulder, bruises, sprains and the like)
- Mild hypertension, 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
- Cuts, peripheral circulation disorders, cold sensitivity, depressed mood, dry skin
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.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.