Seto Yuka Onsen
Analysis UnverifiedSeto Yuka Onsen rises at the foot of Mt. Yuka overlooking the Seto Inland Sea. According to local accounts, an analysis by the national Tokyo Hygienic Laboratory in 1914 (Taisho 3) confirmed that this source is a radon-bearing radioactive spring. Its pale yellow-brown, neutral water soothes gently while the radon-laden steam lingers in the air, letting the body loosen from within. It suits pilgrims visiting the Yuka Shrine and anyone seeking a quiet, restorative soak.
The bar length shows how abundant each component is compared to thresholds that make it "distinctive" (therapeutic spring standards, beauty spring criteria, etc.).
A rare radioactive spring where trace radiation absorbed via inhalation and skin is expected to stimulate cells (the "hormesis effect").
- Metasilicic acid50.2 mg/kg
- Feel
- Your skin may feel smoother.
- Said to
- 50 mg/kg or more is said to mark a “skin-beautifying spring”; it is also used in skincare.
- Note
- The “skin-beautifying” label is a common rule of thumb, not a legal standard.
Effects are general descriptions based on the Ministry of the Environment’s indications by spring type, not a guarantee.
Scores are calculated from mineral analysis data based on the Mineral Spring Analysis Guidelines (Ministry of Environment, Japan). They are unrelated to facility atmosphere or service quality.
▸Note
The temperature, pH and component values shown here are based on the hot spring analysis (source). Actual values in the bath may differ depending on heating, dilution, recycling and filtration. Please check current usage status at the facility.
The 18.8°C source is heated before use. Since radon is absorbed mainly through the steam, breathe slowly and deeply in the bathhouse and stay in moderately warm water for about 10 to 15 minutes.
With about 282 Bq/kg of radon (76.2×10⁻¹⁰ Ci/kg), this radioactive spring is traditionally associated with helping to relieve pain and may support immune system stimulation through mild low-dose stimulation, suiting those with neuralgia, stiff joints or chilly hands and feet.
Avoid bathing during acute illness or with serious heart, lung or kidney conditions. Do not bathe right after meals or drinking, and drink water before and after bathing.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Seto Yuka Onsen
- Spring type
- Simple Weakly radioactive Cold Mineral Spring
- Source temperature
- 18.8℃
- pH
- 6.7
- Osmotic pressure
- 低張性
Analysis Document
- Analysis date
- 2017-02-28
- Analyst organization
- 公益財団法人岡山県健康づくり財団
- Registration No.
- 岡山県自第1号
Cations
- Sodium ion Na⁺
- 26.0 mg/kg
- Potassium ion K⁺
- 1.1 mg/kg
- Magnesium ion Mg²⁺
- 1.0 mg/kg
- Calcium ion Ca²⁺
- 17.0 mg/kg
- Aluminum ion Al³⁺
- < 0.1 mg/kg
- Manganese ion Mn²⁺
- 0.19 mg/kg
- Iron(II) ion Fe²⁺
- 3.0 mg/kg
- Zinc ion Zn²⁺
- < 0.01 mg/kg
- Lead ion Pb²⁺
- < 0.01 mg/kg
- Copper ion Cu²⁺
- < 0.01 mg/kg
- Cadmium ion Cd²⁺
- < 0.005 mg/kg
- Total cations
- 48.1 mg/kg
Anions
- Fluoride ion F⁻
- 2.4 mg/kg
- Chloride ion Cl⁻
- 9.7 mg/kg
- Hydrogen sulfide ion HS⁻
- < 0.2 mg/kg
- Sulfate ion SO₄²⁻
- 4.4 mg/kg
- Bicarbonate ion HCO₃⁻
- 110 mg/kg
- Carbonate ion CO₃²⁻
- < 0.1 mg/kg
- Total anions
- 126 mg/kg
Undissociated Components
- Metasilicic acid H₂SiO₃
- 50.2 mg/kg
- Total undissociated
- 50.2 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- < 0.1 mg/kg
- Free hydrogen sulfide H₂S
- < 0.2 mg/kg
Trace Components
- Radon Rn
- 281.9 Bq/kg
Totals
- Evaporation residue
- 107 mg/kg
Usage
- Usage status
- Unknown
Indications & Contraindications
- Bathing indications
- Hyperuricemia (gout), Rheumatoid arthritis, Ankylosing spondylitis
- General indications
- High blood pressure (mild), Autonomic instability, Insomnia, Depression, Chronic pain or stiffness in muscles and joints, Muscle stiffness due to motor paralysis, Gastrointestinal dysfunction
- Contraindications
- Acute illness (especially with fever), Active tuberculosis, Malignant tumors, Severe heart disease, Respiratory failure, Renal failure, Bleeding disorders, Severe anemia, Any actively progressing illness, Pregnancy (especially early and late stages), Undergoing radiation therapy, pregnancy (radioactive springs)
Drinking
- Drinkability
- Not drinkable
