Nikawa Spring
Analysis UnverifiedThe Nikawa Source, cherished since ancient times in Kusatsu Onsen, one of Japan's Three Great Hot Springs, lives up to its name, "Nikawa" (boiling river), with intensely bubbling waters. It features a tingling sensation on the skin and a distinctive sulfur aroma. The bracingly hot waters permeate the body and mind, melting away stiffness. After bathing, expect remarkably refreshed skin and a feeling of lightness. It offers rejuvenation from chronic fatigue and deep relaxation from daily stress.
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 natural moisturizer also used in skincare lotions. Forms a thin veil on the skin to reduce moisture loss after bathing.
Mild antibacterial action keeps the skin clean. Trace transdermal absorption supports tooth and bone health.
- Sulfur5.1 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 2.06
- 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)303 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.
- Sulfate669 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 acid237 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 temperature48.8℃
- 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 its potent pH 2.06 strong-acid composition, first-time bathers and those with sensitive skin should begin with brief 3–5 minute immersions. Rinse thoroughly with warm water afterward to cleanse residual acidic minerals from the skin. As tolerance builds, divide soaks into 2–3 sessions daily for optimal therapeutic effect. Never forget to hydrate with a full cup of water before and after each bath.
The spring's extreme pH 2.06 acidity, combined with sulfate ions (669 mg/kg) and aluminum ions (48.2 mg/kg), gently dissolves excess skin keratin, offering remarkable relief for atopic dermatitis, psoriasis, and chronic eczema sufferers. Dissolved hydrogen sulfide (5.4 mg/kg) invigorates circulation, targeting chronic joint and muscle rigidity with lasting comfort. At 48.8°C, this abundantly hot spring's thermal energy supports improved glucose tolerance and peripheral circulation—a blessing for those managing diabetes and circulation disorders.
Those with hypersensitive skin or mucous membranes, and elderly persons prone to xerosis, should refrain from bathing. For delicate complexions, post-bath rinsing with warm water is especially critical to remove mineral deposits and prevent irritation.
※ See the analysis data below for detailed contraindications
ANALYSIS DATAView all analysis fields ▼
Source Info
- Source name
- Nikawa Spring
- Spring type
- Acidic sulfur-containing aluminum sulfate chloride spring (hydrogen sulfide type)
- Old spring type name
- 低張性酸性高温泉
- Source temperature
- 48.8℃
- pH
- 2.06
- Flow type
- Natural spring
- Osmotic pressure
- Hypotonic
Analysis Document
- Analysis date
- 2023-08-04
- 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.
- 群馬薬第2号
Cations
- Hydrogen ion H⁺
- 8.7 mg/kg
- Sodium ion Na⁺
- 62.7 mg/kg
- Potassium ion K⁺
- 25.1 mg/kg
- Ammonium ion NH₄⁺
- 0.20 mg/kg
- Magnesium ion Mg²⁺
- 38.0 mg/kg
- Calcium ion Ca²⁺
- 77.6 mg/kg
- Aluminum ion Al³⁺
- 48.2 mg/kg
- Manganese ion Mn²⁺
- 1.9 mg/kg
- Iron(II) ion Fe²⁺
- 17.3 mg/kg
- Total cations
- 280 mg/kg
Anions
- Fluoride ion F⁻
- 9.3 mg/kg
- Chloride ion Cl⁻
- 303 mg/kg
- Sulfate ion SO₄²⁻
- 669 mg/kg
- Hydrogen sulfate HSO₄⁻
- 196 mg/kg
- Total anions
- 1178 mg/kg
Undissociated Components
- Metasilicic acid H₂SiO₃
- 237 mg/kg
- Metaboric acid HBO₂
- 8.5 mg/kg
- Total undissociated
- 249 mg/kg
Dissolved Gas
- Free carbon dioxide CO₂
- 95.4 mg/kg
- Free hydrogen sulfide H₂S
- 5.4 mg/kg
- Total dissolved gas
- 101 mg/kg
Totals
- Total dissolved substances
- 1710 mg/kg
- Component total
- 1810 mg/kg
- Evaporation residue
- 1540 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
