A simple sulfur spring of the hydrogen-sulfide type. The water runs colorless, clear and tasteless at the wellhead but carries the faint rotten-egg note of H₂S that gives a sulfur spring its signature. Mineralization is light at 298 mg/kg and the reaction is weakly acidic, so the bath feels gentle rather than sharp, while 72.7 mg/kg of metasilicic acid leaves the skin noticeably smoother. The posted certificate documents the water for atopic dermatitis, psoriasis vulgaris, chronic eczema, pyoderma and peripheral circulation disorders. Bathing only — the panel states that drinking requires permission from the public health office.
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
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
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
- Active stage of any illness (especially with fever)
- Active tuberculosis
- Marked physical debilitation, such as advanced malignant tumor or severe anemia
- Severe heart or lung disease causing breathlessness on slight exertion
- Severe kidney disease accompanied by edema
- Gastrointestinal bleeding
- Visible bleeding
- Acute exacerbation of a chronic illness
- People with sensitive skin or mucous membranes
- Dry skin in the elderly
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⁺25.6mgP6 national35%
- Magnesiummild; a laxative if you drink itMg²⁺12.4mgP64 national32%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺16.4mgP35 national26%
- Potassiumminor; matters for drinking limitsK⁺5.8mgP37 national5%
- Aluminumshows up in acidic volcanic waterAl³⁺0.40mgP74 national1%
- AmmoniumNH₄⁺0.20mgP30 national0.3%
- ZincZn²⁺< —mg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻105mgP43 national56%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻42.2mgP37 national29%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻15.7mgP16 national14%
- NitrateNO₃⁻0.60mgP63 national0.3%
- H2PO4H₂PO₄⁻0.20mgP57 national0.0%
- Hydrogen sulfideHS⁻0.10mgP28 national0.0%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃72.7mgP45 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂0.30mgP7 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂420mgP94 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S2.4mgP82 national
- ArsenicAs0.0020mgP8 national
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
- Chronic muscle or joint pain and stiffness (rheumatoid arthritis, osteoarthritis, lower back pain, neuralgia, frozen shoulder, bruises, sprains — chronic phase)
- Cold sensitivity
- Reduced gastrointestinal function (heaviness, bloating)
- Impaired glucose tolerance (diabetes)
- Mild hypercholesterolemia
- Mild asthma or emphysema
- Stress-related symptoms (sleep disorders, depressed mood)
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.
- 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.
- 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