1-go Otsu Sen
Analysis VerifiedIchigo Otsu-sen, a symbol of Noboribetsu Onsen, naturally gushes approximately 1,900 liters per minute from Jigokudani (Hell Valley). Its distinct sulfur aroma and milky white waters have historically soothed countless balneotherapy visitors. With a pH of 2.3, this strongly acidic spring offers a sensation that tightens the skin and gently warms the body to its core, truly a blessing from the earth. Still cherished by many hot spring facilities in town, this water supports those seeking to reset their mind and body and achieve 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.
A trace component with gentle antibacterial and anti-inflammatory action.
An iron-rich spring whose water turns yellow-brown to red-brown when exposed to air. Strong heat retention.
- Sulfur10.4 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 2.3
- 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.
- Iron26.6 mg/kg
- Feel
- Turns reddish-brown in the air, with a rusty-iron smell.
- Said to
- Said to warm the body; where drinking is permitted, said to help iron-deficiency anemia.
- Note
- May stain white towels and swimwear.
- Metasilicic acid76.6 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 temperature72.5℃
- 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.
At 72.5°C, Issho-Otsusen is exceptionally hot and highly acidic, making it a vigorous bathing experience. Rinse gently with fresh water after bathing to clear mineral residue from your skin. Avoid prolonged soaks and drink water frequently to stay hydrated throughout your visit.
Rich with pH 2.3 acidic strength and abundant sulfur compounds, this source is renowned for its powerful antimicrobial action on atopic dermatitis and chronic eczema. Its iron content delivers a deep, lingering warmth that radiates through the body long after bathing. Ideal for weekend wellness retreats seeking to revitalize fatigued muscles and spirits.
The strong acidity demands caution for sensitive-skinned individuals and elderly guests with dry skin—risk of thermal shock and irritation exists. Bathing is contraindicated during fever or for those with severe cardiac conditions.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- 1-go Otsu Sen
- Spring type
- 酸性・含硫黄・鉄（Ⅱ, Ⅲ）－単純温泉（硫化水素型）
- Old spring type name
- 含硫化水素－酸性緑ばん泉
- Source temperature
- 72.5℃
- pH
- 2.3
- Flow rate
- 1,901 L/min
- Flow type
- 自然湧出
- Osmotic pressure
- 低張性
Analysis Document
- Analysis date
- 2019-07-02
- Analyst organization
- 北海道立衛生研究所
- Registration No.
- 北海道第1号
Cations
- Hydrogen ion H⁺
- 5.0 mg/kg
- Sodium ion Na⁺
- 36.0 mg/kg
- Potassium ion K⁺
- 5.6 mg/kg
- Ammonium ion NH₄⁺
- 1.3 mg/kg
- Magnesium ion Mg²⁺
- 5.7 mg/kg
- Calcium ion Ca²⁺
- 20.1 mg/kg
- Aluminum ion Al³⁺
- 29.1 mg/kg
- Iron(II) ion Fe²⁺
- 22.0 mg/kg
- Iron(III) ion Fe³⁺
- 4.6 mg/kg
- Total cations
- 129 mg/kg
Anions
- Fluoride ion F⁻
- 0.10 mg/kg
- Chloride ion Cl⁻
- 7.9 mg/kg
- Hydrogen sulfide ion HS⁻
- 0.00 mg/kg
- Thiosulfate ion S₂O₃²⁻
- 3.3 mg/kg
- Sulfate ion SO₄²⁻
- 543 mg/kg
- Bicarbonate ion HCO₃⁻
- 0.00 mg/kg
- Carbonate ion CO₃²⁻
- 0.00 mg/kg
- Bromide ion Br⁻
- 0.00 mg/kg
- Iodide ion I⁻
- 0.00 mg/kg
- Hydrogen sulfate HSO₄⁻
- 91.7 mg/kg
- Dihydrogen phosphate H₂PO₄⁻
- 0.40 mg/kg
- Total anions
- 646 mg/kg
Undissociated Components
- Sulfuric acid H₂SO₄
- 1.2 mg/kg
- Arsenious acid HAsO₂
- 0.20 mg/kg
- Metasilicic acid H₂SiO₃
- 76.6 mg/kg
- Metaboric acid HBO₂
- 21.3 mg/kg
- Total undissociated
- 99.3 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 44.0 mg/kg
- Free hydrogen sulfide H₂S
- 9.1 mg/kg
- Total dissolved gas
- 53.1 mg/kg
Trace Components
- Radon Rn
- 0.72 Bq/kg
Totals
- Total dissolved substances
- 875 mg/kg
- Component total
- 928 mg/kg
- Evaporation residue
- 952 mg/kg
Usage
- Heating
- No
- Dilution
- Yes
- Recycle / Filter
- No
- Additives
- No
- Disinfection
- No
Indications & Contraindications
- Bathing indications
- Atopic dermatitis, Plaque psoriasis, Chronic eczema, Epidermal suppuration, Impaired glucose tolerance (diabetes), Autonomic instability, Insomnia, Depression
- General indications
- High blood pressure (mild), Rheumatoid arthritis, 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
