単純温泉

Under 1,000 mg/kg of dissolved solids, at 25°C or above at the source. Being dilute, it is the gentlest of the ten classes — little sting, little risk of 湯あたり (bathing fatigue) — which makes it the usual recommendation for children, older bathers, and anyone who likes to soak for a long time. Where the pH is high it is labelled アルカリ性単純温泉 and has a distinctly silky feel on the skin.

What it is like

Colourless, effectively odourless and tasteless. Alkaline examples feel slippery, almost soapy, between the fingers.

Indications (適応症)

Autonomic instability, insomnia, low mood

Contraindications (禁忌症)

No contraindications specific to this class. The general ones still apply: acute illness, fever, serious heart disease, and active bleeding.

適応症 and 禁忌症 are the claims a certificate is permitted to state under the Hot Spring Act. They are not medical advice, and nothing here is. If you have a heart condition, are pregnant, or are unwell, ask a doctor rather than a guidebook.