Ashinoyu Onsen Ashikari-no-yu (Register No. Ashinoyu 9)
Analysis UnverifiedKnown as a healing spa since the Kamakura era and counted among Hakone's Seven Springs in Edo times, Ashinoyu sits on a high marshland. This clear 58.6°C water carries white sulfur flakes and a hydrogen-sulfide aroma, combining sulfur, sulfate and bicarbonate traits with 219 mg/kg of metasilicic acid—a quiet mountain bath for those seeking smooth skin.
The bar length shows how abundant each component is compared to thresholds that make it "distinctive" (therapeutic spring standards, beauty spring criteria, etc.).
A natural moisturizer also used in skincare lotions. Forms a thin veil on the skin to reduce moisture loss after bathing.
The aroma typical of sulfur springs, with circulatory and antibacterial effects.
Transdermal absorption gently supports skin hydration and muscle relaxation.
- Sulfur25.2 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.
- Bicarbonate (baking soda)221 mg/kg
- Feel
- Your skin feels smooth and silky.
- Said to
- Said to remove old skin cells and excess sebum. Bathing indications include cuts, poor circulation and dry skin.
- Note
- It can leave skin dry—moisturize after bathing.
- Sulfate355 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 acid219 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 temperature58.6℃
- 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.
The water contains hydrogen sulfide, so keep the bathroom ventilated and avoid putting your face close to the surface. Remove silver jewelry, which the sulfur tarnishes, and moisturize afterward—sulfur water can dry the skin.
Bicarbonate (221 mg/kg) at pH 8.1 softens old skin cells while 219 mg/kg of metasilicic acid leaves silky skin. Sulfate (355 mg/kg) and calcium (109 mg/kg) may support a restorative warmth that lingers long after the bath.
The water contains hydrogen sulfide—keep the room ventilated and avoid inhaling steam deeply. Sensitive skin should be rinsed with fresh water and moisturized afterward.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Ashinoyu Onsen Ashikari-no-yu (Register No. Ashinoyu 9)
- Spring type
- Sulfur-containing Calcium-Sodium-Magnesium Sulfate and Bicarbonate Hot Spring
- Old spring type name
- 含石膏重曹－硫黄泉
- Source temperature
- 58.6℃
- pH
- 8.1
- Osmotic pressure
- 低張性
Analysis Document
- Analysis date
- 2013-08-12
- Analyst organization
- 神奈川県温泉地学研究所
- Registration No.
- 神奈川県知事登録第1号
Cations
- Lithium ion Li⁺
- 0.01 mg/kg
- Sodium ion Na⁺
- 72.0 mg/kg
- Potassium ion K⁺
- 7.5 mg/kg
- Magnesium ion Mg²⁺
- 33.6 mg/kg
- Calcium ion Ca²⁺
- 109 mg/kg
- Aluminum ion Al³⁺
- 0.01 mg/kg
- Manganese ion Mn²⁺
- 0.62 mg/kg
- Iron(II) ion Fe²⁺
- 0.01 mg/kg
- Zinc ion Zn²⁺
- 0.00 mg/kg
- Lead ion Pb²⁺
- 0.00 mg/kg
- Strontium ion Sr²⁺
- 0.03 mg/kg
- Copper ion Cu²⁺
- 0.00 mg/kg
- Cadmium ion Cd²⁺
- 0.00 mg/kg
- Total cations
- 223 mg/kg
Anions
- Fluoride ion F⁻
- 0.00 mg/kg
- Chloride ion Cl⁻
- 4.3 mg/kg
- Hydrogen sulfide ion HS⁻
- 21.5 mg/kg
- Thiosulfate ion S₂O₃²⁻
- 4.4 mg/kg
- Sulfate ion SO₄²⁻
- 355 mg/kg
- Bicarbonate ion HCO₃⁻
- 221 mg/kg
- Carbonate ion CO₃²⁻
- 2.0 mg/kg
- Bromide ion Br⁻
- 0.03 mg/kg
- Iodide ion I⁻
- 0.00 mg/kg
- Nitrate ion NO₃⁻
- 0.00 mg/kg
- Hydrogen metasilicate HSiO₃⁻
- 5.4 mg/kg
- Metaborate ion BO₂⁻
- 0.02 mg/kg
- Total anions
- 614 mg/kg
Undissociated Components
- Metasilicic acid H₂SiO₃
- 219 mg/kg
- Metaboric acid HBO₂
- 0.30 mg/kg
- Total undissociated
- 219 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 3.0 mg/kg
- Free hydrogen sulfide H₂S
- 1.9 mg/kg
- Total dissolved gas
- 4.9 mg/kg
Totals
- Total dissolved substances
- 1056 mg/kg
- Component total
- 1061 mg/kg
- Evaporation residue
- 891 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, 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
