Shirahata Spring
Analysis UnverifiedShirahatage Genzen, located in Kusatsu Onsen and adjacent to Yubatake (Kusatsu's central hot-water field), is said to have been discovered by Minamoto no Yoritomo. Historically, it served as the stage for 'Jikan-yu' (timed bathing), supporting balneotherapy culture, and is truly considered the soul of Kusatsu. Its distinctive aroma and powerful waters, which feel as though they firm the skin, seem to awaken the mind and body from within. Surrendering to its embrace offers a pure moment to shed daily clamor and rediscover one's true self. This spring is a sanctuary for those seeking a fresh start and rejuvenation.
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 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)328 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.
- Sulfate686 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 acid241 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 temperature51.9℃
- 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 intense acidity (pH 2.05), begin with short immersions of 3–5 minutes to gauge your skin's response, gradually extending to 15–20 minutes. After bathing, resist the urge to rinse immediately; instead, gently pat dry with a towel and rest warmly to allow mineral compounds to linger and penetrate deeper. Those with particularly sensitive skin should rinse promptly if irritation arises.
With a spring temperature of 51.9℃ and a powerful pH of 2.05, this sulfur-rich acidic spring delivers 685.5 mg/kg sulfate ions and 328.1 mg/kg chloride ions, alongside 6.4 mg/kg free hydrogen sulfide—a potent formula for treating dermatological conditions. The synergy of intense acidity and sulfur compounds bactericizes and softens skin layers, making it especially cherished by those battling atopic dermatitis, psoriasis, and chronic eczema. Its scope of benefit extends to chronic pain (joint rheumatism, lower back pain, neuralgia), autonomic nervous system imbalance, and stress-induced sleep disorders.
Those with hypersensitive skin or mucous membranes, elderly individuals with dry skin conditions, and those with serious cardiac, pulmonary, or renal disease should refrain from bathing. Its strong acidity demands that sensitive-skinned bathers rinse thoroughly with warm water post-immersion. Bathing is contraindicated during active hemorrhage or fever.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Shirahata Spring
- Spring type
- Acidic sulfurous aluminum sulfate chloride spring (hydrogen sulfide type) (hypotonic acidic hot spring)
- Source temperature
- 51.9℃
- 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⁺
- 9.3 mg/kg
- Sodium ion Na⁺
- 67.0 mg/kg
- Potassium ion K⁺
- 26.3 mg/kg
- Ammonium ion NH₄⁺
- 0.30 mg/kg
- Magnesium ion Mg²⁺
- 41.2 mg/kg
- Calcium ion Ca²⁺
- 78.0 mg/kg
- Aluminum ion Al³⁺
- 47.1 mg/kg
- Manganese ion Mn²⁺
- 1.9 mg/kg
- Iron(II) ion Fe²⁺
- 18.5 mg/kg
- Total cations
- 290 mg/kg
Anions
- Fluoride ion F⁻
- 10.0 mg/kg
- Chloride ion Cl⁻
- 328 mg/kg
- Sulfate ion SO₄²⁻
- 686 mg/kg
- Hydrogen sulfate HSO₄⁻
- 216 mg/kg
- Total anions
- 1239 mg/kg
Undissociated Components
- Metasilicic acid H₂SiO₃
- 241 mg/kg
- Metaboric acid HBO₂
- 9.6 mg/kg
- Total undissociated
- 255 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 29.3 mg/kg
- Free hydrogen sulfide H₂S
- 6.4 mg/kg
- Total dissolved gas
- 35.7 mg/kg
Totals
- Total dissolved substances
- 1780 mg/kg
- Component total
- 1820 mg/kg
- Evaporation residue
- 1610 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
