A sulfur spring at Yuya Ebisu in the Myoban district of Beppu, drawn from the facility's own well: 95 °C steam from a 55 m bore is blown into the water, so the bath runs faintly whitish and slightly turbid under a strong rotten-egg note of H₂S. The chemistry itself is light — 185 mg/kg of dissolved solids, neutral and hypotonic — but 76.5 mg/kg of metasilicic acid gives the water a soft, smooth touch on the skin, placing it in Japan's beauty-water family. The certificate's sample was taken at the bath itself (the Tsukiyo-no-Usagi rock bath) rather than at the wellhead, and the facility's onsen karte records no dilution, no reheating, no recirculation and no disinfection; drinking is not permitted. Documented bathing uses include chronic skin conditions, chronic gynecological conditions and cuts.
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
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
- Acute illness (especially with fever)
- Active tuberculosis
- Malignant tumor
- Severe heart disease
- Respiratory failure
- Renal failure
- Bleeding disorders
- Severe anemia
- Any other illness in an actively progressing stage
- Pregnancy (especially early and late stages)
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.
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺9.3mgP24 national40%
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺8.6mgP2 national32%
- Magnesiummild; a laxative if you drink itMg²⁺3.2mgP40 national23%
- Potassiumminor; matters for drinking limitsK⁺1.5mgP17 national4%
- Iron (II)Fe²⁺0.20mgP38 national0.9%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻54.9mgP31 national58%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻25.5mgP33 national34%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻3.0mgP4 national5%
- Thiosulfateoxidized sulfurS₂O₃²⁻2.7mgP87 national3%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃76.5mgP45 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂103mgP79 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S6.8mgP88 national
Measured at the source
On the certificate
- Diabetes
- Neuralgia
- Muscle pain
- Joint pain
- Frozen shoulder
- Motor paralysis
- Joint stiffness
- Bruises
- Sprains
- Chronic digestive disorders
- Cold sensitivity
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.
- 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