A sodium bicarbonate-chloride cold mineral spring. Sodium supplies 95% of the cations and bicarbonate runs to 1,020 mg/kg, which places the water firmly in the juso-sen (soda-water) style; weakly alkaline and soft on the skin, it belongs to Japan's beauty-water family. The source emerges at only 20.5 °C, so it is a cold mineral spring that has to be reheated for bathing, and at the wellhead it is colorless but faintly cloudy with a light hydrogen sulfide note. The certificate's appendix documents it for cuts, peripheral circulation disorders, dry skin and cold sensitivity.
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
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 conditions involving marked physical debilitation
- Severe heart or lung disease causing breathlessness on slight exertion
- Severe kidney disease accompanied by edema
- Gastrointestinal bleeding
- Any 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⁺437mgP74 national95%
- Potassiumminor; matters for drinking limitsK⁺13.3mgP51 national2%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺5.4mgP18 national1%
- MagnesiumMg²⁺1.8mgP34 national0.7%
- LithiumLi⁺0.70mgP63 national0.5%
- Iron (III)Fe³⁺0.60mgP81 national0.2%
- Iron (II)Fe²⁺0.30mgP43 national0.1%
- AluminumAl³⁺0.0000mg0.0%
- BariumBa²⁺0.0000mg0.0%
- CopperCu²⁺0.0000mg0.0%
- HydrogenH⁺0.0000mg0.0%
- ManganeseMn²⁺0.0000mg0.0%
- StrontiumSr²⁺0.0000mg0.0%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻1,020mgP91 national75%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻194mgP55 national25%
- FluorideF⁻1.3mgP52 national0.3%
- SulfateSO₄²⁻1.4mgP9 national0.1%
- BromideBr⁻0.30mgP37 national0.0%
- AsO2AsO₂⁻0.0000mg0.0%
- BO2BO₂⁻0.0000mg0.0%
- CarbonateCO₃²⁻0.0000mg0.0%
- Hydrogen sulfideHS⁻0.0000mg0.0%
- HSiO3HSiO₃⁻0.0000mg0.0%
- IodideI⁻0.0000mg0.0%
- HydroxideOH⁻0.0000mg0.0%
- SS²⁻0.0000mg0.0%
- ThiosulfateS₂O₃²⁻0.0000mg0.0%
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂26.8mgP78 national
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃19.5mgP4 national
- Metaarsenious acidHAsO₂0.0000mg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂58.0mgP71 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.0000mg
- ArsenicAs< —mg
- CadmiumCd< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
- Chronic muscle or joint pain and stiffness (rheumatoid arthritis, osteoarthritis, lower back pain, neuralgia, frozen shoulder, bruises, sprains — chronic phase)
- Muscle stiffness associated with motor paralysis
- Reduced gastrointestinal function (heaviness, bloating)
- Mild hypertension
- Impaired glucose tolerance (diabetes)
- Mild hypercholesterolemia
- Mild asthma or emphysema
- Hemorrhoid pain
- Stress-related symptoms (sleep disorders, depressed mood)
- Peripheral circulation disorders
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.
- 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.