Nanatsuishi Onsen is posted as a simple sulfur spring — lightly mineralized, earning its therapeutic-spring status on sulfur content alone, and carrying the unmistakable rotten-egg note of H₂S that marks the type. The notice lists it for neuralgia and muscle and joint pain, and — squarely in the sulfur spring's own register — for skin complaints, cuts, and diabetes. The same notice is unusually plain about the flip side: people with sensitive skin or mucous membranes are named among the contraindications, a caution particular to sulfur water.
Good for
Skin conditions
Sulfur and acidic waters are antibacterial and keratolytic, studied for atopic dermatitis and psoriasis.
atopic skin, eczema
Circulation
Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.
tired legs
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
Sensitive-skin caution
Strongly acidic or sulfur-rich water can sting broken, atopic-flare, or dry elderly skin. Ease in slowly and rinse off if it stings.
broken or dry skin
The analysis date is not recorded on our copy of the certificate.
This list uses the wording the Ministry of the Environment replaced in 2014, so it may not match a current certificate.
- Tuberculosis
- Malignant tumor
- Anemia
- Renal failure
- Respiratory failure
- People with sensitive skin or mucous membranes
On the certificate
The analysis date is not recorded on our copy of the certificate.
This list uses the wording the Ministry of the Environment replaced in 2014, so it may not match a current certificate.
- Neuralgia
- Muscle and joint pain
- Hemorrhoids
- Diabetes
- Skin conditions
- Bruises
- Sprains
- Cold injury (frostbite)
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.
- 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.
- Akiyama H et al. Antimicrobial effects of acidic hot-spring water on S. aureus. J. Dermatological Science 24(3):193–200, 2000.
- 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.
- Ministry of the Environment, Japan. 禁忌症及び入浴又は飲用上の注意事項 (2014 notice).official