Oku no Yu Gensen
Analysis VerifiedOkunoyu, a naturally gushing source within Noboribetsu Onsen, emerges from the swamp bottom adjacent to Oyunuma, a crater lake formed by the eruption of Mt. Hiyoriyama. The grayish-black or milky-white cloudy waters, gushing from its 'fuki' vents, along with the rising steam and sulfurous aroma, transport visitors to an extraordinary realm. Its waters gently envelop the skin, and the chloride spring's veil provides a restorative warmth that lingers from the body's core. This source is highly recommended for those seeking to feel the earth's powerful energy and achieve deep relaxation, releasing both mental and physical fatigue.
The bar length shows how abundant each component is compared to thresholds that make it "distinctive" (therapeutic spring standards, beauty spring criteria, etc.).
Undissociated boric acid with antibacterial action that keeps the skin surface clean.
The source of the distinctive sulfur smell. Dilates blood vessels via skin and inhalation to strongly boost circulation.
- Sulfur15.5 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.
- Chloride (salt)709 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.
- Metasilicic acid93.9 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 temperature64.2℃
- 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.
Because the source temperature is extremely high, the water is naturally cooled to comfortable bathing temperature as it travels through facility pipes. The weakly acidic sulfur-rich waters may irritate sensitive skin; after bathing, we recommend rinsing gently with cool shower water to minimize irritation and preserve the thermal experience.
At pH 3.8 with 709.4 mg/kg dissolved chloride ions, these weakly acidic waters purify the skin while the salt content forms an invisible thermal barrier against heat loss. Ideal for those suffering from peripheral circulation disorders or chronic cold sensitivity, this mineral composition warms the body's core, dissolving daily fatigue and tension with remarkable efficacy.
Those with sensitive skin or mucous membranes, and elderly visitors with dry skin conditions, should exercise caution before bathing. This source water is not suitable for drinking.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Oku no Yu Gensen
- Spring type
- 含硫黄－ナトリウム・カルシウム－塩化物温泉 (硫化水素型)
- Old spring type name
- 含塩化土類－食塩硫化水素泉
- Source temperature
- 64.2℃
- pH
- 3.8
- Flow rate
- 75 L/min
- Flow type
- 自然湧出
- Osmotic pressure
- 低張性
Analysis Document
- Analysis date
- 2018-06-29
- Analyst organization
- 北海道立衛生研究所
- Registration No.
- 北海道第1号
Cations
- Hydrogen ion H⁺
- 0.20 mg/kg
- Sodium ion Na⁺
- 267 mg/kg
- Potassium ion K⁺
- 79.9 mg/kg
- Ammonium ion NH₄⁺
- 0.10 mg/kg
- Magnesium ion Mg²⁺
- 4.9 mg/kg
- Calcium ion Ca²⁺
- 124 mg/kg
- Aluminum ion Al³⁺
- 1.0 mg/kg
- Manganese ion Mn²⁺
- 1.8 mg/kg
- Iron(II) ion Fe²⁺
- 2.2 mg/kg
- Iron(III) ion Fe³⁺
- 0.00 mg/kg
- Lead ion Pb²⁺
- 0.00 mg/kg
- Total cations
- 482 mg/kg
Anions
- Fluoride ion F⁻
- 0.20 mg/kg
- Chloride ion Cl⁻
- 709 mg/kg
- Hydrogen sulfide ion HS⁻
- 0.00 mg/kg
- Thiosulfate ion S₂O₃²⁻
- 11.4 mg/kg
- Sulfate ion SO₄²⁻
- 46.6 mg/kg
- Bicarbonate ion HCO₃⁻
- 0.00 mg/kg
- Carbonate ion CO₃²⁻
- 0.00 mg/kg
- Bromide ion Br⁻
- 5.8 mg/kg
- Iodide ion I⁻
- 1.3 mg/kg
- Hydrogen sulfate HSO₄⁻
- 0.20 mg/kg
- Total anions
- 775 mg/kg
Undissociated Components
- Arsenious acid HAsO₂
- 0.50 mg/kg
- Metasilicic acid H₂SiO₃
- 93.9 mg/kg
- Metaboric acid HBO₂
- 51.7 mg/kg
- Total undissociated
- 146 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 141 mg/kg
- Free hydrogen sulfide H₂S
- 9.6 mg/kg
- Total dissolved gas
- 151 mg/kg
Totals
- Total dissolved substances
- 1403 mg/kg
- Component total
- 1554 mg/kg
- Evaporation residue
- 1688 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, 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)
Drinking
- Drinkability
- Not drinkable
