A simple thermal spring of the hypotonic, weakly alkaline, high-temperature class rising in Isawa-cho, Fuefuki. Weakly alkaline and gentle on the skin, it belongs to the Japanese beauty-water family with a soft, low-irritation feel. The certificate lists it for stiff muscles and joints, sensitivity to cold, and recovery from fatigue.
Good for
Aches & joints
Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.
stiff shoulders
Smooth skin
Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.
dry, rough skin
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
- Active phase of illness (especially when fever is present)
- Active tuberculosis
- Advanced malignant tumors or severe anemia and other cases of marked physical debility
- Severe heart or lung disease causing breathlessness on slight exertion
- Severe kidney disease accompanied by edema
- Gastrointestinal bleeding
- When there is visible bleeding
- Acute exacerbation of a chronic illness
Measured at the source
On the certificate
- Chronic pain or stiffness of muscles or joints (chronic phase of rheumatoid arthritis, osteoarthritis, lower back pain, neuralgia, frozen shoulder, bruises, sprains)
- Sensitivity to cold
- Peripheral circulatory disturbance
- Weak gastrointestinal function (heaviness in the stomach, gas in the intestines)
- Mild hypertension
- Impaired glucose tolerance (diabetes mellitus)
- Mild hypercholesterolemia
- Mild asthma or emphysema
- Hemorrhoidal pain
- Various stress-related symptoms (sleep disorders, depressive states, etc.)
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.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
- Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
- Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.