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, nettō 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
- 病気の活動期(特に熱のあるとき)
- 活動性の結核、進行した悪性腫瘍又は重篤な貧血などの全身衰弱の著しい場合
- 少し動くと息苦しくなるような重い心肺疾患の状態
- 消化管出血、目に見える出血があるとき
- 慢性疾患の急性増悪期
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.
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺542mgP92 national56%
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺471mgP74 national43%
- Potassiumminor; matters for drinking limitsK⁺19.1mgP62 national1%
- LithiumLi⁺0.40mgP49 national0.1%
- StrontiumSr²⁺1.7mgP82 national0.1%
- MagnesiumMg²⁺0.80mgP25 national0.0%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻903mgP78 national54%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻1,019mgP96 national45%
- BicarbonateHCO₃⁻11.6mgP6 national0.4%
- FluorideF⁻0.70mgP41 national0.1%
- BromideBr⁻2.4mgP72 national0.1%
- Iodideyellows in air; helps blood lipidsI⁻0.10mgP40 national
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃52.1mgP32 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂25.1mgP77 national
- Metaarsenious acidHAsO₂0.60mgP86 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
- 筋肉又は関節の慢性的な痛みまたはこわばり(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)
- 胃腸機能の低下(胃もたれ、腸にガスがたまるなど)
- Impaired glucose tolerance (diabetes)
- Mild hypercholesterolemia
- Mild asthma or emphysema
- きりきず、末梢循環障害、冷え性、うつ状態、皮膚乾燥症
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.