Kunoshima Onsen on Ookunoshima island — classified as a weakly radioactive simple cold-mineral spring (hypotonic, neutral, cold-mineral). The wellhead emerges at just 19.5 °C, so the water is reheated for bathing rather than served at source temperature. Mineralization is light at 130 mg/kg of dissolved solids, which keeps the feel gentle and unobtrusive on the skin. The classification places it in the radon-spring family, the tradition associated with the so-called hormesis claim, and the certificate flags type-specific indications for gout, rheumatoid arthritis and ankylosing spondylitis.
Good for
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
From a certificate analyzed in 2016.
- Active stage of any illness (especially with fever)
- Active tuberculosis
- Advanced malignant tumor, severe anemia or other marked physical weakness
- Severe heart or lung disease causing shortness of breath on slight exertion
- Severe kidney disease with edema
- Gastrointestinal bleeding
- Visible bleeding
- Acute exacerbation of a chronic illness
Full composition
The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺14.5mgP3 national51%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺10.0mgP26 national41%
- Magnesiummild; a laxative if you drink itMg²⁺1.1mgP27 national7%
- PotassiumK⁺0.60mgP7 national0.8%
- StrontiumSr²⁺0.02mgP11 national
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻39.1mgP26 national50%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻9.7mgP12 national21%
- Fluoridetrace; drinking limits applyF⁻4.4mgP75 national18%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻6.3mgP17 national10%
- NitrateNO₃⁻0.30mgP49 national0.8%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃42.8mgP23 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂4.9mgP28 national
- ArsenicAsNDmg
- CopperCuNDmg
- Mercurytoxic trace — part of the drinking-safety checkHgNDmg
- LeadPbNDmg
Measured at the source
On the certificate
From a certificate analyzed in 2016.
- Chronic muscle or joint pain or stiffness (the chronic phase of osteoarthritis, lower back pain, neuralgia, frozen shoulder, bruises, sprains and the like)
- Muscle stiffness associated with motor paralysis
- Cold sensitivity
- Peripheral circulation disorders
- Reduced gastrointestinal function (bloating)
- Mild hypertension
- Impaired glucose tolerance (diabetes)
- Mild hypercholesterolemia
- Mild asthma or emphysema
- Hemorrhoid pain
- Stress-related sleep disorders and depressed mood
- Hyperuricemia (gout)
- Rheumatoid arthritis
- Ankylosing spondylitis