Nishinokawara Gensen (Cho-yu)
Analysis UnverifiedSainokawara Source, a prominent representative of Kusatsu Onsen, is a historic hot spring cherished by therapeutic bathers for centuries. Nestled amidst the mystical steam of Sainokawara Park, it offers a pleasant, skin-tightening sensation and a powerful warmth that permeates to the very core, providing restorative warmth. After a soak, a remarkable lightness awaits. For those seeking to alleviate skin concerns, chronic fatigue, or to achieve deep relaxation and reset mind and body from daily stress, this source provides a moment to connect with nature's revitalizing energy.
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.
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.
- Acidic (pH)pH 2.04
- 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)416 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.
- Sulfate722 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 acid278 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 temperature53.7℃
- 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.
Due to the strongly acidic pH of 2.04, those with sensitive skin are advised to rinse off with fresh water after bathing. First-time bathers should start with 3–5 minutes and gradually extend to 10–15 minutes as they acclimate. Since the source temperature is 53.7°C, always take a thorough pre-bath rinse, and rest for at least 30 minutes after each session.
With a pH of 2.04, a source temperature of 53.7°C, and high concentrations of sulfate (721.5 mg/kg) and chloride (416.3 mg/kg), this spring is officially indicated for skin conditions such as atopic dermatitis, chronic eczema, and psoriasis, as well as cuts, poor circulation, and cold sensitivity. It is also recognized for relieving chronic pain from rheumatoid arthritis, lower back pain, and neuralgia.
Those with sensitive skin or mucous membranes, and elderly individuals with dry skin conditions, should avoid bathing. Due to the strong acidity, people with delicate skin are advised to rinse off with fresh water after bathing.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Nishinokawara Gensen (Cho-yu)
- Spring type
- Acidic aluminum sulfate chloride spring (Hypotonic acidic high-temperature spring)
- Source temperature
- 53.7℃
- pH
- 2.04
- 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⁺
- 80.6 mg/kg
- Potassium ion K⁺
- 34.2 mg/kg
- Ammonium ion NH₄⁺
- 0.30 mg/kg
- Magnesium ion Mg²⁺
- 51.7 mg/kg
- Calcium ion Ca²⁺
- 99.8 mg/kg
- Aluminum ion Al³⁺
- 55.8 mg/kg
- Manganese ion Mn²⁺
- 2.4 mg/kg
- Iron(II) ion Fe²⁺
- 16.5 mg/kg
- Lead ion Pb²⁺
- 0.00 mg/kg
- Copper ion Cu²⁺
- 0.00 mg/kg
- Total cations
- 351 mg/kg
Anions
- Fluoride ion F⁻
- 13.6 mg/kg
- Chloride ion Cl⁻
- 416 mg/kg
- Sulfate ion SO₄²⁻
- 722 mg/kg
- Hydrogen sulfate HSO₄⁻
- 232 mg/kg
- Total anions
- 1384 mg/kg
Undissociated Components
- Sulfuric acid H₂SO₄
- 5.6 mg/kg
- Metasilicic acid H₂SiO₃
- 278 mg/kg
- Metaboric acid HBO₂
- 12.4 mg/kg
- Total undissociated
- 296 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 66.0 mg/kg
- Free hydrogen sulfide H₂S
- 0.00 mg/kg
- Total dissolved gas
- 66.0 mg/kg
Trace Components
- Total sulfur S
- 0.89 mg/kg
Totals
- Total dissolved substances
- 2030 mg/kg
- Component total
- 2100 mg/kg
- Evaporation residue
- 1830 mg/kg
Usage
- Heating
- No
- Dilution
- Yes（Water dilution for temperature adjustment. As the source spring temperature is extremely high at 94.5-96°C, water dilution is performed to lower the temperature to levels suitable for drinking. While some facilities specify "no water dilution or heating" on official websites, water dilution is typically included during heat exchange in the distribution system.）
- Recycle / Filter
- No
- Additives
- No
- Disinfection
- No
Indications & Contraindications
- Bathing indications
- Atopic dermatitis, Plaque psoriasis, 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), Sensitive skin or mucous membranes, eye conditions (acidic springs)
Drinking
- Drinkability
- Not drinkable
