A gentle alkaline simple thermal spring, drilled in June 1990 beside the Maze River in Gero, Gifu. At pH 9.72 it is strongly alkaline, and with only 208 mg/kg of dissolved solids the water is lightly mineralized — the combination gives the slippery, soap-like feel that places it in Japan's beauty-water family, a claim the facility's own panel repeats. The certificate documents the water for neuralgia, muscle and joint pain, cold sensitivity and fatigue recovery. The source feeds fifteen different baths here, among them an open-air bath set above the river and its greenery.
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 2019.
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.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺67.4mgP20 national97%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺1.7mgP6 national3%
- PotassiumK⁺0.40mgP4 national0.4%
- Iron (II)Fe²⁺0.03mgP14 national0.0%
- Aluminumshows up in acidic volcanic waterAl³⁺NDmg
- Manganesetrace; companion to iron springsMn²⁺NDmg
- Fluoridetrace; drinking limits applyF⁻19.9mgP98 national34%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻48.6mgP92 national26%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻10.1mgP12 national9%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻14.3mgP10 national8%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻7.6mgP18 national5%
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂29.1mgP59 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂SNDmg
- ArsenicAs0.05mgP50 national
Measured at the source
On the certificate
From a certificate analyzed in 2019.
This list uses the wording the Ministry of the Environment replaced in 2014, so it may not match a current certificate.
- Neuralgia
- Muscle pain
- Joint pain
- Frozen shoulder
- Motor paralysis
- Joint stiffness
- Bruises
- Sprains
- Chronic digestive disorders
- Hemorrhoids
- Cold sensitivity
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.