曹Bicarbonate
A bicarbonate spring carrying sodium, magnesium, and calcium, and also a carbon-dioxide-bearing source. The bicarbonate character gives it a soft, skin-smoothing feel of the Japanese beauty-water family. The certificate lists cuts, poor peripheral circulation, sensitivity to cold, and dry skin among its spring-specific bathing indications.
Good for
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
On the certificate:dry skin
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
On the certificate:autonomic nervous instabilityconvalescence after illnessrecovery from fatiguehealth promotion
Take care
Contraindications
- active phase of illness (especially with fever)
- active tuberculosis
- advanced malignant tumors or severe anemia and other marked physical debilitation
- severe heart or lung disease causing breathlessness on slight exertion
- severe kidney disease with edema
- gastrointestinal bleeding
- presence of visible bleeding
- acute exacerbation of a chronic illness
On the certificate
- cuts and abrasions
- poor peripheral circulation
- sensitivity to cold
- chronic pain or stiffness of muscles and joints
- muscle stiffness associated with motor paralysis
- weak gastrointestinal function
- mild hypertension
- impaired glucose tolerance (diabetes)
- mild hypercholesterolemia
- mild asthma or emphysema
- hemorrhoidal pain
- stress-related symptoms (sleep disturbance, 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.
- 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.