A sulfur-bearing sodium chloride-sulfate spring, and one of the hottest natural sources in the country. Free hydrogen sulfide and hydrosulfide together carry the unmistakable rotten-egg note of H₂S, while 2,268 mg/kg of dissolved solids — chloride and sulfate leading — give the water noticeable body. Metasilicic acid at 109.4 mg/kg leaves the kind of thin silica film that makes skin feel smoother afterwards, and the posting lists atopic dermatitis, psoriasis vulgaris, chronic eczema and pyoderma among its documented indications.
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
Warming
Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, netto 熱の湯).
cold sensitivity
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
- Advanced malignant tumors, severe anemia, or other states of marked physical debilitation
- Severe heart or lung disease causing breathlessness on slight exertion
- Severe kidney disease accompanied by edema
- Gastrointestinal bleeding
- Any 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⁺635mgP80 national
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺62.3mgP62 national
- Potassiumminor; matters for drinking limitsK⁺61.7mgP87 national
- Magnesiummild; a laxative if you drink itMg²⁺1.8mgP33 national
- Manganesetrace; companion to iron springsMn²⁺0.50mgP65 national
- LithiumLi⁺0.40mgP48 national
- FeTotalFe0.04mgP21 national
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻769mgP80 national
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻326mgP75 national
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻186mgP56 national
- Fluoridetrace; drinking limits applyF⁻4.1mgP73 national
- Hydrogen sulfidesulfur character — antibacterialHS⁻3.5mgP82 national
- Bromidetrace, sea-originBr⁻2.5mgP75 national
- Hydrogen phosphateHPO₄²⁻0.90mgP81 national
- Iodideyellows in air; helps blood lipidsI⁻0.30mgP61 national
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃109mgP58 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂100mgP96 national
- Metaarsenious acidHAsO₂3.3mgP98 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂43.0mgP66 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S5.1mgP85 national
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)
- 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.
- Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
- 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