A sodium-led bicarbonate spring with sulfate quietly filling out the body — the classic jūsō-sen style emerging hot at 56 degrees Celsius. At the wellhead it carries a faint sulfur note and a slight metallic edge on the tongue, while a neutral pH keeps the touch soft and places it in Japan's beauty-water family. A generous 168.8 mg/kg of metasilicic acid leaves the kind of silica film that makes skin feel noticeably smoother afterwards.
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
Circulation
Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.
tired legs
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
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
- 別表による
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⁺288mgP62 national73%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺60.2mgP61 national17%
- Magnesiummild; a laxative if you drink itMg²⁺11.3mgP63 national5%
- Potassiumminor; matters for drinking limitsK⁺16.1mgP55 national2%
- AmmoniumNH₄⁺2.5mgP84 national0.8%
- LithiumLi⁺0.80mgP68 national0.7%
- Iron (II)Fe²⁺2.4mgP75 national0.2%
- AluminumAl³⁺0.09mgP39 national0.1%
- BariumBa²⁺0.10mgP50 national0.0%
- Manganesetrace; companion to iron springsMn²⁺0.09mgP25 national
- ZincZn²⁺0.04mgP66 national
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻551mgP79 national62%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻146mgP61 national21%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻84.7mgP36 national17%
- FluorideF⁻0.10mgP8 national0.1%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃169mgP76 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂15.1mgP68 national
- Metaarsenious acidHAsO₂0.10mgP54 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂75.1mgP75 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂SNDmg
- ChromiumCr< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
- 別表による
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.
- Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
- 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.