Value Village ／ Health
This answer is a draft. It stays unpublished until legal review and source verification are complete.
"Air conditioning is bad for you" and *reibō-byō* (冷房病, "air-con sickness") are phrases heard all over Japan, and visitors ask why Japanese people seem to dislike air conditioning. Meanwhile, about 40% of heatstroke cases happen indoors. Here we sort out how to use air conditioning, based on public sources.
| Item | Detail | Source |
|---|---|---|
| Where heatstroke happens | The home, about 40%, is the most common place (ambulance call-outs) | Fire and Disaster Management Agency (2023, 2024) |
| Heatstroke deaths | About 80% aged 65 or over; most indoor deaths were in homes where air conditioning was not in use or not installed | Tokyo Medical Examiner's Office; MHLW |
| Ministry of the Environment guide | Aim for a room temperature of 28°C (room temperature, not the set temperature); use air conditioning rather than putting up with the heat | Ministry of the Environment heatstroke prevention site |
| "Reibō-byō" | Not a medical diagnosis. A popular term for feeling unwell from over-cooling, temperature swings and dry air | — |
| Temperature difference | General explanations say the strain on the body rises when the gap to outdoors reaches 5–7°C or more | — |
| Cause of feeling unwell | Measure |
|---|---|
| Cold air blowing directly on the body | Point the vanes upwards and circulate the air with a fan |
| Set temperature too low (women in offices often feel cold) | Room temperature 26–28°C; a cardigan, a lap blanket, socks |
| Dry air | Humidify; drink fluids regularly |
| Gap to the outdoor temperature | Turn the cooling down before going out; pause a moment at the door |
| Not moving | Sitting still under air conditioning lowers blood flow. Move once an hour |
[Verify] Check the share by location against the FDMA heatstroke statistics, the pattern of deaths against the Tokyo Medical Examiner's Office publications, and the room-temperature guide against Ministry of the Environment material.
Most heatstroke deaths happen indoors where air conditioning was not in use. Using it is what protects your health. Deal with discomfort through settings and airflow direction.
28°C is a guide for room temperature, not the set temperature. Check with a thermometer in the room, and if humidity is high, go a little lower.
The opposite. Older people feel heat less and sweat less, so they slip into heatstroke without noticing. "Air conditioning even if you do not feel hot"; more families living apart now keep watch remotely with a thermometer-linked monitor.
Air conditioning itself does not cause infections. Chill and dry air can lower the body's defences, so avoid direct airflow, humidify, and switch it off or use the timer at night (but night-time heatstroke also happens, so on hot nights the Ministry of the Environment's advice is to leave it on low).
When the air is hot, a fan only blows hot air at you. The Ministry of the Environment recommends air conditioning once room temperature passes 28°C. Use the fan to support the air conditioning (circulating the air).
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https://www.wbgt.env.go.jp/
https://www.fdma.go.jp/disaster/heatstroke/post3.html
https://www.hokeniryo.metro.tokyo.lg.jp/kansatsu/
⚠️ 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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