Dorogawa Onsen Shinsen is a weakly alkaline (pH 8.29) simple thermal spring, low-temperature at 29 °C at the wellhead. Lightly mineralized at 0.241 g/kg, it is gentle on the body and soft on the skin. The water runs clear and colorless with almost no taste or odor — a quiet, undemanding bath.
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
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 removed from the official list of contraindications then, or include a condition that was. If you have a health condition, ask a doctor before bathing.
- 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) (dropped from the official list in 2014)
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⁺62.9mgP18 national91%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺5.1mgP18 national8%
- MagnesiumMg²⁺0.30mgP16 national0.6%
- PotassiumK⁺0.60mgP7 national0.3%
- Aluminumshows up in acidic volcanic waterAl³⁺< —mg
- BariumBa²⁺< —mg
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺< —mg
- LithiumLi⁺< —mg
- Manganesetrace; companion to iron springsMn²⁺< —mg
- AmmoniumNH₄⁺< —mg
- StrontiumSr²⁺< —mg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻95.0mgP43 national50%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻24.0mgP17 national22%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻18.1mgP62 national19%
- Fluoridetrace; drinking limits applyF⁻3.3mgP67 national5%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻3.3mgP13 national2%
- Hydrogen phosphateHPO₄²⁻2.5mgP89 national1.0%
- Hydrogen sulfideHS⁻0.80mgP65 national0.6%
- BromideBr⁻0.60mgP50 national0.3%
- Iodideyellows in air; helps blood lipidsI⁻< —mg
- NitrateNO₃⁻< —mg
- Thiosulfateoxidized sulfurS₂O₃²⁻< —mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃22.4mgP7 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂2.2mgP20 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂3.7mgP25 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S< —mg
- ArsenicAs0.02mgP36 national
- CopperCu0.0040mgP48 national
- CadmiumCd< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
- Radonfaint radon — studied for joint pain (hormesis)Rn< —mg
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.
- 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.