Ichi-go Ko-sen
Analysis VerifiedThis is one of the most well-known sources in Noboribetsu, a leading onsen destination in Hokkaido. It continuously flows at a high temperature of 96.5°C, embodying the raw power of the earth. The highly acidic water, with a pH of 2.2, provides a tingling sensation on the skin and a refreshing feeling after bathing. Its rich iron and sulfate content offers a powerful bathing experience that feels as if it's awakening both mind and body. It's a spring for those who wish to reset from daily fatigue, gain new vitality, and feel nature's energy throughout their entire being.
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.
Strong astringent action that tightens skin. A key component of acidic springs, suited to oily or acne-prone skin.
A natural moisturizer also used in skincare lotions. Forms a thin veil on the skin to reduce moisture loss after bathing.
- Acidic (pH)pH 2.2
- 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.
- Iron26.7 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.
- Chloride (salt)215 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.
- Sulfate648 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 acid149 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 temperature96.5℃
- 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.
With a highly acidic pH of 2.2, these waters are very stimulating, so those with sensitive skin should be cautious. Avoid long soaks; start with a short bath of 3-5 minutes. It's recommended to lightly rinse off the spring water with a shower after bathing.
The highly acidic pH 2.2 spring is traditionally associated with supporting skin issues like atopic dermatitis, thanks to its cleansing properties, and may support immune system stimulation. Rich in iron ions (Fe²⁺ 8.6mg/kg, Fe³⁺ 18.1mg/kg) and sulfate ions (647.8mg/kg), it is also recommended for those experiencing poor circulation or sensitivity to cold.
Individuals with sensitive skin or mucous membranes, and elderly people with dry skin should avoid bathing. This water is not for drinking.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Ichi-go Ko-sen
- Spring type
- Acidic Iron(II,III)-containing Sodium Sulfate and Chloride Hot Spring
- Old spring type name
- 含食塩-芒硝酸性緑ばん泉
- Source temperature
- 96.5℃
- pH
- 2.2
- Flow rate
- 67 L/min
- Flow type
- Natural spring
- Osmotic pressure
- Hypotonic
Analysis Document
- Analysis date
- 2018-03-09
- Analyst organization
- 北海道立衛生研究所
- Registration No.
- 北海道第1号
Cations
- Hydrogen ion H⁺
- 6.3 mg/kg
- Sodium ion Na⁺
- 158 mg/kg
- Potassium ion K⁺
- 18.3 mg/kg
- Ammonium ion NH₄⁺
- 3.5 mg/kg
- Magnesium ion Mg²⁺
- 20.7 mg/kg
- Calcium ion Ca²⁺
- 44.1 mg/kg
- Aluminum ion Al³⁺
- 16.9 mg/kg
- Manganese ion Mn²⁺
- 0.40 mg/kg
- Iron(II) ion Fe²⁺
- 8.6 mg/kg
- Iron(III) ion Fe³⁺
- 18.1 mg/kg
- Zinc ion Zn²⁺
- 0.01 mg/kg
- Lead ion Pb²⁺
- 0.00 mg/kg
- Copper ion Cu²⁺
- 0.00 mg/kg
- Cadmium ion Cd²⁺
- 0.00 mg/kg
- Total cations
- 295 mg/kg
Anions
- Chloride ion Cl⁻
- 215 mg/kg
- Hydroxide ion OH⁻
- 0.00 mg/kg
- Hydrogen sulfide ion HS⁻
- 0.20 mg/kg
- Thiosulfate ion S₂O₃²⁻
- 0.00 mg/kg
- Sulfate ion SO₄²⁻
- 648 mg/kg
- Bicarbonate ion HCO₃⁻
- 0.00 mg/kg
- Carbonate ion CO₃²⁻
- 0.00 mg/kg
- Hydrogen sulfate HSO₄⁻
- 138 mg/kg
- Dihydrogen phosphate H₂PO₄⁻
- 0.20 mg/kg
- Total anions
- 1001 mg/kg
Undissociated Components
- Sulfuric acid H₂SO₄
- 2.2 mg/kg
- Arsenious acid HAsO₂
- 0.80 mg/kg
- Metasilicic acid H₂SiO₃
- 149 mg/kg
- Metaboric acid HBO₂
- 195 mg/kg
- Total undissociated
- 347 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 77.0 mg/kg
- Free hydrogen sulfide H₂S
- 0.40 mg/kg
- Total dissolved gas
- 77.4 mg/kg
Totals
- Total dissolved substances
- 1643 mg/kg
- Component total
- 1720 mg/kg
- Evaporation residue
- 1723 mg/kg
Usage
- Heating
- No
- Dilution
- Yes（源泉温度が高いため、ほぼ全ての浴槽で加水して湯温調整）
- 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
- Drinking notes
- この温泉は飲用に利用しない。
