What are the maximum temperatures bearable by the human body?

Rather than a temperature from which the human body would no longer be able to withstand heat, it is rather a combination of factors, such as humidity, duration of exposure or even the state person’s health.

Heat felt differently

To estimate the maximum bearable temperature, the humidity level is one of the indicators to be taken into account. This rate represents the ratio between the quantity of water vapor in the air, and the maximum quantity of water vapor that the air can contain. The transpiration mechanism no longer works when this number reaches 100%, as it does not evaporate.

It becomes impossible for the human body to regulate its temperature in this way. In 2010, this threshold was set at 35°C for a humidity level of 100%, 46°C for a humidity level reduced by half. Values ​​questioned by scientists from Penn State University in the United States, who have just published their work in the journal International Journal of Biometeorology.

“In addition to humidity, age, the person’s state of health, particularly on the cardiovascular level, and their resistance to dehydration also come into play. emphasizes Dr Gérald Kierzek, emergency doctor and medical director of Doctissimo.

Laboratory conditions

To reach their conclusions, the researchers put healthy volunteers, men and women, under real temperature conditions in order to subject them to “heat stress in a controlled environment”.

To establish the internal temperature of the participants, they had to swallow a video capsule that continuously measured their body temperature. They then simulated a typical day in this laboratory, with the temperature and humidity levels being regulated by the scientists. This is how they were able to measure the body temperature of each volunteer and estimate that the new limit for the human body is 31°C for 100% humidity.

Less effective regulatory mechanisms

Under these conditions, the exposure of individuals should not last more than a few hours. Indeed, at these levels of humidity, the temperature regulation mechanisms no longer work perfectly, such as perspiration and increased skin blood flow to evacuate heat from the body.

In France, the humidity levels have never reached such levels but in some countries, such as India or Pakistan for example, the climatic conditions combine these two factors and create deadly heat/humidity waves for people older people in particular.

What to do in case of extreme heat?

The first reflex to have, in case of strong heat, is to stay cool and at rest. Dr. Gérald Kierzek recalls the essential points to implement during a heat wave:

• Close the shutters during the day, to keep as much freshness as possible;
• Remember to hydrate and limit your efforts;
• Go to the cinema, museum, libraries and all air-conditioned places;
• Stay well hydrated on a regular basis.

Finally, the doctor recalls, “pay attention to the effects of certain cardiovascular or neurotropic drugs which can affect the body’s ability to regulate heat”.