A sodium-calcium chloride spring rising at a notably hot 65.8 °C — among the hotter natural sources documented in the region. The water is moderately mineralized (around 2,800 mg/kg evaporation residue) with a salty, heat-retaining character, weakly alkaline and gentle on the skin, and leaves a faint mineral film on emerging.
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
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(特に熱のあるもの)
- Active tuberculosis
- 進行した悪性腫瘍又は高度の貧血などのみられる重い病気
- 少し動くと息苦しくなるなど重い心肺の病気
- むくみのあるような重い腎臓の病気
- 消化管出血
- 目に見える出血があるとき
- 慢性の病気の急性増悪期
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.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺598mgP78 national
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺240mgP86 national
- Potassiumminor; matters for drinking limitsK⁺12.3mgP49 national
- Magnesiummild; a laxative if you drink itMg²⁺6.3mgP56 national
- LithiumLi⁺0.60mgP56 national
- StrontiumSr²⁺0.29mgP46 national
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺0.03mgP13 national
- BariumBa²⁺0.01mgP31 national
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- Iron (III)Fe³⁺< —mg
- Manganesetrace; companion to iron springsMn²⁺< —mg
- AmmoniumNH₄⁺< —mg
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻1,303mgP82 national
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻117mgP57 national
- Bromidetrace, sea-originBr⁻3.0mgP76 national
- Iodideyellows in air; helps blood lipidsI⁻1.9mgP88 national
- NitrateNO₃⁻0.37mgP43 national
- Thiosulfateoxidized sulfurS₂O₃²⁻0.02mgP31 national
- Fluoridetrace; drinking limits applyF⁻< —mg
- Hydrogen sulfidesulfur character — antibacterialHS⁻< —mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃62.7mgP38 national
- ChromiumCr0.20mgP100 national
- CopperCu0.0020mgP42 national
- LeadPb0.0003mgP17 national
- CadmiumCd< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
Measured at the source
On the certificate
- Chronic digestive disorders
- Hemorrhoids
- 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.
- 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.