Jizo no Yu Spring (Prefectural)
Analysis UnverifiedNestled in Kusatsu Onsen, one of Japan's three most renowned hot springs, Jizo-no-yu has been cherished since ancient times, deeply intertwined with Kusatsu's unique `yumomi` (hot water stirring) culture. This powerful spring, known for its invigorating touch, seems to cleanse away physical and mental stagnation. It provides a deep, restorative warmth that penetrates to the core, offering a refreshing sensation akin to rejuvenation after your bath. Jizo-no-yu offers solace to travelers seeking relief from persistent fatigue or skin discomfort, and those desiring an authentic hot spring experience.
The bar length shows how abundant each component is compared to thresholds that make it "distinctive" (therapeutic spring standards, beauty spring criteria, etc.).
Strong astringent action that tightens skin. A key component of acidic springs, suited to oily or acne-prone skin.
The source of the distinctive sulfur smell. Dilates blood vessels via skin and inhalation to strongly boost circulation.
Mild antibacterial action keeps the skin clean. Trace transdermal absorption supports tooth and bone health.
A natural moisturizer also used in skincare lotions. Forms a thin veil on the skin to reduce moisture loss after bathing.
A trace component with gentle antibacterial and anti-inflammatory action.
- Sulfur6.5 mg/kg
- Feel
- Smells like boiled eggs; the water may turn milky white or blue-green.
- Said to
- Said to be strongly antibacterial and to promote circulation. Bathing indications include atopic dermatitis and chronic eczema.
- Note
- With sensitive skin, rinse with fresh water after bathing. Remove silver jewelry—it tarnishes.
- Acidic (pH)pH 2
- Feel
- May tingle on the skin; tastes sour.
- Said to
- Said to be strongly antibacterial. Bathing indications include atopic dermatitis and plaque psoriasis.
- Note
- Can irritate sensitive skin—rinse with fresh water after bathing. Keep it out of your eyes.
- Chloride (salt)314 mg/kg
- Feel
- Tastes salty; the warmth lasts after you get out.
- Said to
- Salt is said to form a film on the skin that keeps in heat and moisture. Bathing indications include cuts, poor circulation and dry skin.
- Note
- May sting cuts. Strong salty water can tire you—avoid long soaks.
- Sulfate679 mg/kg
- Feel
- Your skin feels moist; the water may taste slightly bitter.
- Said to
- Said to retain heat well and help heal cuts. Bathing indications include cuts and dry skin.
- Note
- It warms you well—do not stay in too long.
- Metasilicic acid234 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.
- Source temperature50.1℃
- Feel
- The source is 42°C or hotter; the bath may be on the hot side.
- Said to
- Heat is said to boost circulation and warm the body.
- Note
- Older people and those with high blood pressure or heart conditions should avoid baths of 42°C or more. Keep soaks short.
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.
Given its formidable pH 2.0 acidic nature, Jizou-no-yu demands measured approach. Begin with brief immersions of 3–5 minutes; even with acclimatization, limit sessions to 10–15 minutes maximum. Rinse thoroughly in warm water immediately after bathing to remove mineral residue—essential for those with sensitive skin. Start with 1–2 baths daily, monitoring for thermal irritation as you gradually adjust frequency.
At pH 2.0 with spring temperature of 50.1°C, this water carries 678.5 mg/kg sulfate ions and 314.1 mg/kg chloride ions, delivering potent antimicrobial and keratin-softening properties. Those battling atopic dermatitis, chronic eczema, and psoriasis report particular relief. The 6.9 mg/kg free hydrogen sulfide boosts circulation, alleviating cold intolerance, peripheral vascular dysfunction, and chronic muscular and joint stiffness.
Avoid bathing if you have hypersensitive skin or mucous membranes, or if you experience age-related skin dryness. The strong acidity necessitates rinsing in warm water post-bathing, especially for sensitive-skinned bathers.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Jizo no Yu Spring (Prefectural)
- Spring type
- Acidic sulfurous aluminum sulfate-chloride spring (hydrogen sulfide type) (low-osmotic acidic high-temperature spring)
- Source temperature
- 50.1℃
- pH
- 2
- Flow type
- Natural spring
- Osmotic pressure
- Hypotonic
Analysis Document
- Analysis date
- 2023-08-04
- Analyst organization
- 一般社団法人 群馬県薬剤師会（環境衛生試験センター）
- Registration No.
- 群馬薬第2号
Cations
- Hydrogen ion H⁺
- 9.6 mg/kg
- Sodium ion Na⁺
- 62.9 mg/kg
- Potassium ion K⁺
- 25.7 mg/kg
- Ammonium ion NH₄⁺
- 0.30 mg/kg
- Magnesium ion Mg²⁺
- 39.6 mg/kg
- Calcium ion Ca²⁺
- 73.6 mg/kg
- Aluminum ion Al³⁺
- 46.2 mg/kg
- Manganese ion Mn²⁺
- 1.9 mg/kg
- Iron(II) ion Fe²⁺
- 18.3 mg/kg
- Total cations
- 278 mg/kg
Anions
- Fluoride ion F⁻
- 9.6 mg/kg
- Chloride ion Cl⁻
- 314 mg/kg
- Sulfate ion SO₄²⁻
- 679 mg/kg
- Hydrogen sulfate HSO₄⁻
- 218 mg/kg
- Total anions
- 1220 mg/kg
Undissociated Components
- Metasilicic acid H₂SiO₃
- 234 mg/kg
- Metaboric acid HBO₂
- 9.8 mg/kg
- Total undissociated
- 249 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 57.2 mg/kg
- Free hydrogen sulfide H₂S
- 6.9 mg/kg
- Total dissolved gas
- 64.1 mg/kg
Totals
- Total dissolved substances
- 1750 mg/kg
- Component total
- 1810 mg/kg
- Evaporation residue
- 1580 mg/kg
Usage
- Heating
- No
- Dilution
- No
- Recycle / Filter
- No
- Additives
- No
- Disinfection
- No
Indications & Contraindications
- Bathing indications
- Atopic dermatitis, Plaque psoriasis, Chronic eczema, Epidermal suppuration, Impaired glucose tolerance (diabetes), Cuts and grazes, Peripheral circulatory failure, Poor circulation, Depression, Xeroderma
- General indications
- High blood pressure (mild), Rheumatoid arthritis, Autonomic instability, Insomnia, 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), Severe chronic dermatitis (sulphur springs), Sensitive skin or mucous membranes, eye conditions (acidic springs)
Drinking
- Drinkability
- Not drinkable
