Well No. 2 at Enzan Onsen is a simple sulfur cold-mineral spring with strongly alkaline character (pH 10.1). Source temperature is just 23.8 degC, so it is a cold-mineral spring heated for bathing rather than served at the wellhead. Total dissolved solids are light at 169 mg/kg, but the water carries hydrogen sulfide ions enough to leave a faint sulfurous taste and rotten-egg note at the source. The strong alkalinity gives the pronounced slippery 'beauty-water' feel, the family this spring belongs to.
Good for
Skin conditions
Sulfur and acidic waters are antibacterial and keratolytic, studied for atopic dermatitis and psoriasis.
atopic skin, eczema
Circulation
Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.
tired legs
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
Sensitive-skin caution
Strongly acidic or sulfur-rich water can sting broken, atopic-flare, or dry elderly skin. Ease in slowly and rinse off if it stings.
broken or dry skin
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⁺45.9mgP12 national96%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺1.1mgP3 national2%
- LithiumLi⁺0.06mgP18 national0.4%
- PotassiumK⁺0.30mgP3 national0.4%
- ManganeseMn²⁺0.05mgP22 national0.2%
- Iron (III)Fe³⁺0.04mgP53 national0.1%
- MagnesiumMg²⁺0.01mgP4 national0.1%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻27.0mgP81 national34%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻36.0mgP20 national22%
- HSiO3HSiO₃⁻35.8mgP76 national17%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻11.6mgP14 national12%
- Hydrogen sulfidesulfur character — antibacterialHS⁻2.1mgP79 national4%
- Hydrogen phosphateHPO₄²⁻4.1mgP93 national3%
- Fluoridetrace; drinking limits applyF⁻1.8mgP56 national3%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻2.4mgP11 national3%
- BO2BO₂⁻1.1mgP62 national1%
- AsO2AsO₂⁻0.03mgP77 national0.0%
- ArsenicAs< —mg
- CadmiumCd< —mg
- ChromiumCr< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
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.
- 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.
- Akiyama H et al. Antimicrobial effects of acidic hot-spring water on S. aureus. J. Dermatological Science 24(3):193–200, 2000.
- Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
- 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.
- Ministry of the Environment, Japan. 禁忌症及び入浴又は飲用上の注意事項 (2014 notice).official