A hot (61 °C) chloride-sulfate spring led by calcium and sodium, drawn from the Tsushima No. 22 well. Weakly alkaline (pH 8.4) and soft on the skin, with a moderate 3.05 g/kg of dissolved solids that gives the water noticeable body. Metasilicic acid at 52 mg/kg adds a faint silica-film smoothness — the kind of finish that places it gently in the Japanese 'beauty-water' family.
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
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
From a certificate analyzed in 2021.
- 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
- 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.
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺542mgP94 national56%
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺471mgP76 national43%
- Potassiumminor; matters for drinking limitsK⁺19.1mgP61 national1%
- LithiumLi⁺0.40mgP46 national0.1%
- StrontiumSr²⁺1.7mgP85 national0.1%
- MagnesiumMg²⁺0.80mgP24 national0.0%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻903mgP81 national54%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻1,019mgP96 national45%
- BicarbonateHCO₃⁻11.6mgP7 national0.4%
- FluorideF⁻0.70mgP38 national0.1%
- BromideBr⁻2.4mgP74 national0.1%
- Iodideyellows in air; helps blood lipidsI⁻0.10mgP34 national
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃52.1mgP31 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂25.1mgP77 national
- Metaarsenious acidHAsO₂0.60mgP82 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂0.0000mg
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
Measured at the source
On the certificate
From a certificate analyzed in 2021.
- 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)
- Reduced gastrointestinal function (heaviness, bloating)
- Impaired glucose tolerance (diabetes)
- Mild hypercholesterolemia
- Mild asthma or emphysema
- 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.
- 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.
- 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.