Value Village ／ Health
This answer is a draft. It stays unpublished until legal review and source verification are complete.
Japanese children are taught at school: "when you come home, wash your hands and gargle" (手洗い・うがい, tearai-ugai). Gargling with plain water as a daily habit barely exists outside Japan, and some newcomers doubt it does anything. Here we separate the evidence for each habit, and the way of doing them that actually works.
| Method | Evidence | Guide |
|---|---|---|
| Hand-washing with soap | The most solid evidence for infection prevention. In a Japanese experiment, viruses fell to about 1/100 with running water alone for 15 seconds, and about 1/10,000 with soap for 10 seconds plus running water for 15 seconds (Mori et al., 2006) | Rub for 30 seconds, rinse for 15 seconds |
| Alcohol hand sanitiser | 60–95% ethanol is effective against influenza, COVID-19 and others. Weak against norovirus | A substitute when you cannot wash. Rub in until the hands are dry (about 20 seconds) |
| Water gargling | In a Kyoto University randomised trial (387 people, 2005), the water-gargling group had about 36% fewer colds. The iodine-gargle group showed no significant difference from the control group | When you get home. Rinse the mouth → tilt the head back and gargle for 15 seconds × 2–3 times |
| Masks | The effect of stopping a person with symptoms passing it on is well established. The protective effect for a healthy wearer depends on the situation | Wear one when you have a cough or sneezes |
[Verify] Check the experimental figures of Mori et al. (2006, Kansenshogaku Zasshi) and the reduction rate in the gargling trial of Satomura et al. (2005, American Journal of Preventive Medicine) against the original papers.
Running water alone has about 1/100 of the effect of washing with soap. Soap for 30 seconds, and reach the fingertips, thumbs and wrists.
Alcohol works poorly on visible dirt, norovirus and some bacteria. Hand-washing comes first; alcohol is the back-up.
In the Japanese trial, water gargling showed a benefit and iodine did not. For everyday gargling, water is enough.
Viruses enter the cells within a short time of landing, so the "washing out" effect is limited. Why gargling helps is not fully understood, and regarding it as "a habit on getting home" is the fair position.
Viruses do not die at temperatures your hands can bear. Hot water only causes rough hands. Use lukewarm or cold water and plenty of soap.
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https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/0000191947.html
https://www.jstage.jst.go.jp/article/kansenshogakuzasshi1970/80/5/80_5_496/_article/-char/ja/
https://doi.org/10.1016/j.amepre.2005.06.013
⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.
What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.
This is general information. Results vary from person to person and depend on your own conditions and surroundings.
Please decide for yourself, using your own judgement, whether any of this suits your situation. We cannot accept responsibility for any damage, loss or injury arising from following this article.
This article is not meant to diagnose or manage any specific medical condition. If you are worried about your health, see a doctor rather than relying on your own judgement.
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