A blend of the Nishizawa-no-Yu wells No. 1, 2 and 3 at Ikaho. It is lightly mineralized — about 292 mg/kg of dissolved solids — and neutral in pH, so the water feels gentle rather than assertive, but it carries 74.8 mg/kg of metasilicic acid, the silica that leaves a thin film on the skin and puts this source in Japan's beauty-water family. At 10.7 °C it is a cold-mineral source: it qualifies as an onsen through its metasilicic acid content rather than through heat. The posted notice lists it for convalescence, fatigue recovery and general health improvement.
Good for
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
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
From a certificate analyzed in 1996.
This list uses the wording the Ministry of the Environment replaced in 2014, so it may not match a current certificate. Items marked † were removed from the official list of contraindications then, or include a condition that was. If you have a health condition, ask a doctor before bathing.
- Acute illness (especially with fever)
- Active tuberculosis
- Malignant tumor
- Severe heart disease
- Respiratory failure
- Renal failure
- Bleeding disorders
- Severe anemia
- Any other illness in an actively progressing stage
- Pregnancy (especially the early and late stages) (dropped from the official list in 2014)
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⁺38.9mgP51 national
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺8.5mgP2 national
- Magnesiummild; a laxative if you drink itMg²⁺7.3mgP58 national
- Potassiumminor; matters for drinking limitsK⁺1.5mgP17 national
- Manganesetrace; companion to iron springsMn²⁺0.59mgP66 national
- Aluminumshows up in acidic volcanic waterAl³⁺0.32mgP68 national
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺0.20mgP38 national
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻102mgP44 national
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻51.7mgP41 national
- NitrateNO₃⁻3.1mgP95 national
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻2.9mgP3 national
- Fluoridetrace; drinking limits applyF⁻0.10mgP8 national
- Carbonatestrongly alkaline; slippery feelCO₃²⁻0.0000mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃74.8mgP45 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂0.20mgP6 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂83.9mgP76 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.0000mg
- ArsenicAsNDmg
- CopperCuNDmg
- Mercurytoxic trace — part of the drinking-safety checkHgNDmg
- LeadPbNDmg
Measured at the source
On the certificate
From a certificate analyzed in 1996.
Analyzed before the 2014 revision of the official list, so some wording may be out of date.
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.
- 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.