Value Village ／ Health
This answer is a draft. It stays unpublished until legal review and source verification are complete.
Every winter, Japan's Consumer Affairs Agency and NITE (the National Institute of Technology and Evaluation) issue warnings about "low-temperature burns" from heating devices. They are tied to a distinctly Japanese way of keeping warm: disposable heat packs (カイロ, kairo), hot-water bottles (湯たんぽ, yutanpo), the kotatsu (a low table with a heater underneath and a quilt over it), electric blankets and heated carpets.
| Contact temperature | Rough time to a low-temperature burn |
|---|---|
| 44°C (111°F) | About 3–4 hours |
| 46°C (115°F) | About 30 minutes to 1 hour |
| 50°C (122°F) | About 2–3 minutes |
| Device | Surface temperature | Caution |
|---|---|---|
| Disposable heat pack (kairo) | 40–60°C (peak can exceed 60°C) | Never stick it on bare skin (over clothing), do not use it in bed, do not keep it on one spot for hours |
| Hot-water bottle (yutanpo) | Surface 40–50°C for several hours | Once the bedding is warm, take it out or move it away from your body. A cover is essential |
| Kotatsu | Very hot near the heater | Do not sleep inside it. Keep your feet away from the heater |
| Electric blanket, heated carpet | 40–45°C | Switch off or turn low at bedtime; do not lie on it for hours |
| Electric foot warmer (電気あんか, anka) | Around 50°C | Do not hold it against your body |
| Laptop, phone while charging | Over 40°C | Take care with long periods on your lap or under the covers |
[Verify] Check the temperature and time guidelines and the accident cases against the Consumer Affairs Agency's "Beware of low-temperature burns" and NITE materials.
At 44°C, a few hours damages the deeper skin. Low-temperature burns happen at a "comfortable" temperature.
Sticking it on bare skin is the classic low-temperature burn. Wear it over clothing, move it to a different spot, take it off before sleeping.
Once the bedding is warm, take it out or move it away from your feet. Especially for older people and children.
Low-temperature burns, dehydration and disrupted temperature control. If you are going to sleep, switch it off and go to bed.
Low-temperature burns are often deeper than they look. Cool under running water and see a doctor. Folk fixes (aloe, miso, oil) cause infection.
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https://www.caa.go.jp/policies/policy/consumer_safety/caution/
https://www.nite.go.jp/jiko/chuikanki/
https://www.jsbi-burn.org/
⚠️ 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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