A gentle alkaline simple thermal spring. With its high pH it has the slippery feel of Japan's beauty-water family, soft on the skin. It carries a notable 181.6 mg/kg of metasilicic acid, which leaves a thin silica film for noticeably smoother skin afterwards. The water is reheated and chlorine-disinfected, then served as free-flow.
Good for
Aches & joints
Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.
stiff shoulders
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
- active phase of illness (especially when feverish)
- active tuberculosis
- advanced malignant tumors, severe anemia, or other serious illness
- severe heart or lung disease causing breathlessness on slight exertion
- gastrointestinal bleeding
- any visible bleeding
- acute exacerbation of a chronic illness
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⁺58.9mgP17 national97%
- CalciumCa²⁺0.20mgP0 national0.4%
- Potassiumminor; matters for drinking limitsK⁺2.4mgP24 national
- FeTotalFe< —mg
- Hydrogenmakes the water acidic — sharp and bactericidalH⁺< —mg
- Carbonatestrongly alkaline; slippery feelCO₃²⁻35.3mgP86 national43%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻25.3mgP19 national26%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻31.6mgP19 national19%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻13.2mgP25 national10%
- Hydrogen phosphateHPO₄²⁻1.8mgP88 national1%
- Fluoridetrace; drinking limits applyF⁻0.60mgP38 national1%
- Bromidetrace, sea-originBr⁻< —mg
- Hydrogen sulfidesulfur character — antibacterialHS⁻< —mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃182mgP81 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂0.50mgP8 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂0.0000mg
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.0000mg
Measured at the source
On the certificate
- chronic muscle or joint pain or stiffness
- weak gastrointestinal function
- mild hypertension
- impaired glucose tolerance (diabetes)
- mild hypercholesterolemia
- mild asthma or emphysema
- hemorrhoid pain
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.
- Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
- Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
- 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.