Yubatake Gensen
Analysis VerifiedThe Yubatake source, naturally gushing from Kusatsu Onsen's iconic Yubatake (Kusatsu's central hot-water field), holds a distinguished history. During the Edo period, it was ranked as the highest-ranking Ozeki in the Onsen Banzuke, recognized alongside the Shirahata source as one of Kusatsu's two major hot springs. Its powerful, pH2 water, permeated with a sulfurous aroma, imparts a refreshing, tightening sensation upon the skin. A soak in this historic, renowned hot spring cleanses the body and mind, offering deep relaxation and rejuvenation from daily fatigue. It is a must-visit for those seeking to feel the energy of a historic hot spring and desire a complete refresh.
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.
- Sulfur5.8 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)329 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.
- Sulfate674 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 acid243 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 temperature52.3℃
- 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.
With a highly acidic pH of 2.0, this spring may cause a tingling sensation, especially for those with sensitive skin or the elderly. Avoid long soaks; start with a short dip of about 3 minutes. It is recommended to rinse off with fresh water after bathing.
With a pH of 2.0, its powerful acidity is famously said to "cure everything but a broken heart." Gushing at a hot 52.3°C, the water is sought after for skin conditions like atopic dermatitis and chronic eczema. It's also recommended for improving poor circulation, making it ideal for days when you need to warm up from the core.
Avoid bathing during active phases of illness or if you are physically weak. Due to the strong acidity, individuals with sensitive skin, mucous membranes, or xeroderma in the elderly should be cautious.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Yubatake Gensen
- Spring type
- 酸性・含硫黄-アルミニウム-硫酸塩・塩化物温泉（硫化水素型）
- Source temperature
- 52.3℃
- pH
- 2
- Flow type
- 自然湧出
- Osmotic pressure
- 低張性
Analysis Document
- Analysis date
- 2023-07-25
- 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.
- 群馬藥第2号
Cations
- Hydrogen ion H⁺
- 10.0 mg/kg
- Sodium ion Na⁺
- 59.7 mg/kg
- Potassium ion K⁺
- 30.0 mg/kg
- Ammonium ion NH₄⁺
- 0.50 mg/kg
- Magnesium ion Mg²⁺
- 39.4 mg/kg
- Calcium ion Ca²⁺
- 73.1 mg/kg
- Aluminum ion Al³⁺
- 49.1 mg/kg
- Manganese ion Mn²⁺
- 2.0 mg/kg
- Iron(II) ion Fe²⁺
- 17.8 mg/kg
- Lead ion Pb²⁺
- 0.01 mg/kg
- Total cations
- 282 mg/kg
Anions
- Fluoride ion F⁻
- 10.1 mg/kg
- Chloride ion Cl⁻
- 329 mg/kg
- Sulfate ion SO₄²⁻
- 674 mg/kg
- Hydrogen sulfate HSO₄⁻
- 227 mg/kg
- Total anions
- 1241 mg/kg
Undissociated Components
- Sulfuric acid H₂SO₄
- 5.7 mg/kg
- Metasilicic acid H₂SiO₃
- 243 mg/kg
- Metaboric acid HBO₂
- 9.8 mg/kg
- Total undissociated
- 258 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 46.9 mg/kg
- Free hydrogen sulfide H₂S
- 6.2 mg/kg
- Total dissolved gas
- 53.1 mg/kg
Totals
- Total dissolved substances
- 1780 mg/kg
- Component total
- 1830 mg/kg
- Evaporation residue
- 1620 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
