妙見1号Myoken Spring No.1
A hot (54 °C) sodium-magnesium-calcium bicarbonate spring. The water emerges clear at the wellhead but oxidizes into a faint yellow-brown turbidity on contact with air, leaving a metallic, slightly astringent taste from dissolved iron. Neutral pH and a moderate 2,768 mg/kg mineralization, with an unusually generous 237.5 mg/kg of metasilicic acid that leaves the skin noticeably smoother — the classic silica-film effect.
Good for
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
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
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
- 病気の活動期(特に熱のあるとき)、活動性の結核
- 進行した悪性腫瘍又は高度の貧血など身体衰弱の著しい場合
- 少し動くと息苦しくなるような重い心臓又は肺の病気
- むくみのあるような重い腎臓の病気、消化管出血、目に見える出血があるとき
- 慢性の病気の急性増悪期
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⁺228mgP56 national39%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺157mgP81 national29%
- Magnesiummild; a laxative if you drink itMg²⁺92.8mgP91 national28%
- Potassiumminor; matters for drinking limitsK⁺43.5mgP82 national4%
- LithiumLi⁺1.0mgP74 national0.5%
- AmmoniumNH₄⁺2.3mgP82 national0.5%
- Iron (II)Fe²⁺2.0mgP72 national0.3%
- StrontiumSr²⁺0.20mgP44 national0.0%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻1,251mgP93 national74%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻172mgP52 national17%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻121mgP58 national9%
- Hydrogen phosphateHPO₄²⁻0.40mgP69 national0.0%
- BromideBr⁻0.40mgP39 national0.0%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃238mgP93 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂28.7mgP79 national
- Metaarsenious acidHAsO₂0.20mgP70 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂431mgP95 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.10mgP61 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)
- 運動麻痺における筋肉のこわばり、冷え性、末梢循環障害
- Reduced gastrointestinal function (heaviness, bloating)
- Mild hypertension
- Impaired glucose tolerance (diabetes)
- Mild hypercholesterolemia
- Mild asthma or emphysema
- Hemorrhoid pain
- 自律神経不安定症、ストレスによる諸症状(睡眠障害、うつ状態など)
- Cuts
- Peripheral circulation 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.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- 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.