An 85 C simple sulfur spring of the hydrogen sulfide type, served from one of Kyushu's hotter wellheads. Weakly acidic at pH 5.4, the water carries a distinct moderate sulfur taste and the unmistakable rotten-egg note of H₂S at the source. Total sulfur is 7.8 mg/kg with free H₂S at 7.5 mg/kg, and a generous 164.6 mg/kg of metasilicic acid layers in a faintly silky finish on the skin.
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
From a certificate analyzed in 2017.
This list uses the wording the Ministry of the Environment replaced in 2014, so it may not match a current certificate.
- Acute illness (especially when fever is present)
- Active tuberculosis
- Malignant tumor
- Severe heart disease
- Respiratory failure
- Renal failure
- Bleeding disorders
- Severe anemia
- Any illness in an actively progressing stage
- Kidney disease
- Hypertension
- Any other condition with edema
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⁺92.4mgP26 national67%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺18.1mgP37 national15%
- Potassiumminor; matters for drinking limitsK⁺25.5mgP71 national11%
- Magnesiummild; a laxative if you drink itMg²⁺3.5mgP42 national5%
- LithiumLi⁺0.60mgP59 national1%
- AmmoniumNH₄⁺0.30mgP39 national0.3%
- ManganeseMn²⁺0.60mgP69 national0.3%
- Aluminumshows up in acidic volcanic waterAl³⁺NDmg
- BariumBa²⁺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
- StrontiumSr²⁺NDmg
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻182mgP63 national64%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻62.2mgP30 national30%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻21.0mgP14 national5%
- FluorideF⁻1.0mgP46 national0.8%
- ThiosulfateS₂O₃²⁻0.20mgP52 national0.3%
- Hydrogen sulfideHS⁻0.20mgP36 national0.1%
- BromideBr⁻0.20mgP28 national0.1%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻NDmg
- Hydrogen phosphateHPO₄²⁻NDmg
- Iodideyellows in air; helps blood lipidsI⁻NDmg
- NitrateNO₃⁻NDmg
- HydroxideOH⁻NDmg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃165mgP75 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂4.0mgP29 national
- Metaarsenious acidHAsO₂< —mg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂88.1mgP77 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S7.5mgP90 national
- ChromiumCrNDmg
Measured at the source
On the certificate
From a certificate analyzed in 2017.
This list uses the wording the Ministry of the Environment replaced in 2014, so it may not match a current certificate. Items marked † were dropped from the official list then.
- Bruises
- Chronic digestive disorders
- Cold sensitivity
- Arteriosclerosis
- Chronic digestive disorders
- Chronic constipation
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