Shosen-no-yu is an alkaline simple thermal spring with a pH of 9.42 — high enough to give the slippery, skin-softening feel that places it squarely in the Japanese 'beauty-water' family. Mineralization is light: sodium leads the cation side and bicarbonate accounts for about 70% of the anions, so the water reads as gentle and unobtrusive on the body rather than heavy or salty. Classified as hypotonic, alkaline, low-temperature water in Kyoto's Joyo City, with the usual general indications — neuralgia, muscle and joint pain, stiff shoulder, poor circulation, fatigue recovery — printed on the summary poster.
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
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
- 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
- Pregnancy (especially the 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.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺104mgP30 national98%
- PotassiumK⁺0.50mgP5 national0.6%
- MagnesiumMg²⁺0.02mgP4 national0.6%
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- BariumBa²⁺< —mg
- Hydrogenmakes the water acidic — sharp and bactericidalH⁺< —mg
- LithiumLi⁺< —mg
- AmmoniumNH₄⁺< —mg
- StrontiumSr²⁺< —mg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻211mgP59 national71%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻0.11mgP0 national2%
- FluorideF⁻0.03mgP3 national0.5%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻0.08mgP1 national
- Hydrogen sulfidesulfur character — antibacterialHS⁻< —mg
- Thiosulfateoxidized sulfurS₂O₃²⁻< —mg
Measured at the source
On the certificate
- Neuralgia
- Muscle pain
- Joint pain
- Frozen shoulder
- Motor paralysis
- Joint stiffness
- Bruises
- Sprains
- Chronic digestive disorders
- Hemorrhoids
- 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.
- 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.