A sodium-led chloride-bicarbonate spring, neutral in pH and lightly turbid with a faint yellow-brown tint at the wellhead. The water carries a salty tang and a whiff of hydrogen sulfide, with bicarbonate softness layered into the chloride body. Moderately mineralized at 1,872 mg/kg, it lands in standard onsen-water territory rather than the extremes — a 34.8 °C source heated for bathing in central Kobe.
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
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(特に熱のある場合)
- 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
- 少し動くと息切れがするような重症の心肺疾患の状態
- むくみのあるような腎臓の病気
- 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⁺484mgP75 national82%
- Magnesiummild; a laxative if you drink itMg²⁺24.4mgP73 national8%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺34.2mgP49 national7%
- PotassiumK⁺12.9mgP50 national1.0%
- Iron (II)Fe²⁺0.90mgP61 national0.1%
- ManganeseMn²⁺0.50mgP64 national0.1%
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- BariumBa²⁺< —mg
- LithiumLi⁺< —mg
- AmmoniumNH₄⁺< —mg
- StrontiumSr²⁺< —mg
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻446mgP72 national50%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻751mgP85 national49%
- Bromidetrace, sea-originBr⁻< —mg
- Carbonatestrongly alkaline; slippery feelCO₃²⁻< —mg
- Fluoridetrace; drinking limits applyF⁻< —mg
- Hydrogen sulfidesulfur character — antibacterialHS⁻< —mg
- Iodideyellows in air; helps blood lipidsI⁻< —mg
- Thiosulfateoxidized sulfurS₂O₃²⁻< —mg
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻< —mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃70.1mgP44 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂17.1mgP72 national
- Metaarsenious acidHAsO₂< —mg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂75.7mgP75 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S< —mg
- ArsenicAs< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
- 筋肉若しくは関節の慢性的な痛み又はこわばり(関節リウマチ、変形性関節症、腰痛症、神経痛、五十肩、打撲、捻挫等)
- Muscle stiffness associated with motor paralysis
- Peripheral circulation disorders
- 胃腸機能の低下(胃がもたれ、消化管内ガスがたまる等の場合)
- Mild hypertension
- 耐糖能異常
- Mild hypercholesterolemia
- Mild asthma or emphysema
- Hemorrhoid pain
- ストレスによる諸症状(睡眠障害、うつ状態等)
- 末梢循環障害、冷え性、うつ状態、皮膚乾燥症(泉質別適応症)
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.
- 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.