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Acidic Springs: Powerfully Antibacterial Waters for Skin Conditions

Published May 5, 2026·1min read

Acidic springs contain hydrogen ions at 1 mg/kg or more (typically pH 2–3). Their strong antibacterial action is indicated for atopic dermatitis, plaque psoriasis, and epidermoid suppuration. Note: contraindicated for sensitive skin and elderly guests with dry skin — always confirm before bathing.

Acidic Springs: Powerfully Antibacterial Waters for Skin Conditions
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Table of Contents
  1. What is an Acidic Spring?
  2. Indications for Bathing
  3. How to Bathe in an Acidic Spring

What is an Acidic Spring?

An acidic spring contains hydrogen ions (H⁺) at 1 mg per kilogram of spring water, creating strongly acidic water at roughly pH 2–3 — similar to lemon juice or vinegar. Most are found near volcanic areas; Kusatsu Onsen (Gunma) and Tamagawa Onsen (Akita) are the most famous examples.

The water has very strong antibacterial power; bathing may cause a tingling sensation on the skin, and the water tastes sour. They have traditionally been used as balneotherapy destinations for skin conditions and athlete's foot.

Indications for Bathing

  • Atopic dermatitis
  • Plaque psoriasis
  • Epidermoid suppuration
  • Impaired glucose tolerance (diabetes)

How to Bathe in an Acidic Spring

  1. First-timers: start with 3–5 minutes and monitor your skin before extending the soak.
  2. After bathing, rinse lightly with fresh water — residual acid can be overly irritating.
  3. Shampoo and face wash in a separate bathroom — they react with the acidic water.

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