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
- 病気の活動期(特に熱があるとき)
- Active tuberculosis
- 進行した悪性腫瘍又は高度の貧血など身体衰弱の著しい場合
- 少し動くと息苦しいような重い心臓肺の病気
- 腎不全、肝不全
- 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⁺1,608mgP90 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⁺0.90mgP61 national0.0%
- ManganeseMn²⁺0.50mgP65 national0.0%
- AluminumAl³⁺0.10mgP53 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 healingSO₄²⁻478mgP86 national8%
- FluorideF⁻11.5mgP94 national0.5%
- IodideI⁻0.10mgP35 national0.0%
- Hydrogen phosphateHPO₄²⁻0.0030mgP20 national
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃36.0mgP17 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂10.1mgP56 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂6.6mgP33 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S< —mg
- ArsenicAs0.0050mgP15 national
Measured at the source
On the certificate
- 筋肉や関節のこわばり(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)
- 軽い高血圧、糖尿病、軽症高コレステロール血症
- Mild asthma or emphysema
- Hemorrhoid pain
- 自律神経不安定症、ストレスによる諸症状(睡眠障害、うつ状態など)
- 病後回復期、疲労回復、健康増進
- 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.
- 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.