A simple sulfur spring of the hydrogen-sulfide type, rising among Japan's hottest natural sources. The water runs colorless and clear, yet carries the unmistakable rotten-egg note of H₂S — the certificate records the same odor at the wellhead and again in the lab four hours after sampling. Everything else about the chemistry is light: neutral pH and under a gram per kilogram of dissolved solids, so the body of the water is gentle and it is the sulfur, not the mineral load, that gives it character. Indications and contraindications are not printed here — the certificate defers them to a separate appendix panel that is not part of this record.
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
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
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⁺204mgP52 national71%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺54.4mgP59 national22%
- Potassiumminor; matters for drinking limitsK⁺21.2mgP65 national4%
- Magnesiummild; a laxative if you drink itMg²⁺2.9mgP40 national2%
- LithiumLi⁺0.90mgP71 national1%
- StrontiumSr²⁺1.6mgP84 national0.3%
- AmmoniumNH₄⁺0.60mgP52 national0.2%
- ManganeseMn²⁺0.50mgP66 national0.2%
- BariumBa²⁺0.20mgP72 national
- Aluminumshows up in acidic volcanic waterAl³⁺NDmg
- CopperCu²⁺NDmg
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺NDmg
- Iron (III)Fe³⁺NDmg
- Hydrogenmakes the water acidic — sharp and bactericidalH⁺NDmg
- ZincZn²⁺NDmg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻378mgP70 national51%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻159mgP51 national37%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻60.0mgP45 national10%
- Fluoridetrace; drinking limits applyF⁻4.1mgP72 national2%
- Hydrogen sulfideHS⁻1.6mgP75 national0.4%
- Iodideyellows in air; helps blood lipidsI⁻0.20mgP51 national
- BO2BO₂⁻NDmg
- Bromidetrace, sea-originBr⁻NDmg
- Carbonatestrongly alkaline; slippery feelCO₃²⁻NDmg
- Hydrogen phosphateHPO₄²⁻NDmg
- HSiO3HSiO₃⁻NDmg
- HSO4HSO4NDmg
- NitrateNO₃⁻NDmg
- HydroxideOH⁻NDmg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃23.8mgP8 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂22.6mgP76 national
- H2SO4FreeH2SO4FreeNDmg
- Phosphoric acidH₃PO₄NDmg
- Metaarsenious acidHAsO₂NDmg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂128mgP82 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S6.5mgP88 national
- ArsenicAsNDmg
- CadmiumCdNDmg
- ChromiumCrNDmg
- Mercurytoxic trace — part of the drinking-safety checkHgNDmg
- LeadPbNDmg
Measured at the source
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.
- 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