A hypertonic, strong-salt sodium chloride spring that also carries dissolved carbon dioxide and iron(II) — denser than seawater and leaving a thick mineral coating on the skin. The dissolved iron oxidizes reddish-brown on contact with air, the trademark look of Arima's 'kinsen' (gold) water. The certificate lists indications for poor circulation, sensitivity to cold, and dry skin.
Good for
Circulation
Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.
tired legs
Warming
Salt forms a film on the skin that slows heat loss, so the warmth lingers long after the bath (the classic heat-keeping water, netto 熱の湯).
cold sensitivity
Cuts
Mineral-rich chloride, sulfate and sulfur waters have a long-recorded soothing effect on minor cuts and slow-healing skin.
minor wounds
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
The analysis date is not recorded on our copy of the certificate.
- Active phase of illness (especially when feverish)
- Active tuberculosis
- Advanced malignant tumors or severe physical debilitation such as marked anemia
- Severe heart or lung disease causing breathlessness on slight exertion
- Severe kidney disease with edema
- Gastrointestinal bleeding
- Visible bleeding
- Acute exacerbation of a chronic illness
Measured at the source
On the certificate
The analysis date is not recorded on our copy of the certificate.
- Chronic pain or stiffness of muscles or joints (rheumatoid arthritis, osteoarthritis, lower-back pain, neuralgia, frozen shoulder, and the chronic phase of bruises and sprains)
- Muscle stiffness associated with motor paralysis
- Weakened gastrointestinal function (heaviness in the stomach, intestinal gas, etc.)
- Impaired glucose tolerance (diabetes)
- Mild hypercholesterolemia
- Mild asthma or emphysema
- Various stress-related symptoms (sleep disorders, etc.)
- Dry skin
Evidence
- Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
- Kario K et al. Hemodynamic Effects of Hot Spring Bathing. Hypertension Research 46(3):711–720, 2023.
- Tei C, Kihara T. Waon Therapy for Chronic Heart Failure. J. Cardiology 53(2):214–218, 2009.
- Coavoy-Sánchez SA et al. Hydrogen sulfide and dermatological diseases. Int. J. Dermatology, 2019.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.