Demystifying science | What temperature can humans endure?

Every week, our journalist answers scientific questions from readers.

The answer to this question which fascinates scientists is twofold since humans must monitor two temperatures: that outside, but also that inside their body. According to the literature, people should avoid exposure to outdoor temperatures above 50 ^oC. As for their internal temperature, the debate still rages, but it is rare to see the thermometer exceed 41 ^oC.

As for the outside temperature bearable by a human, generally when we approach 50 ^oC, there may be damage to the skin, says the D^r Waleed Javaid, epidemiologist at Mount Sinai Hospital in New York. And between 40 ^oC and 50 ^oC, there are quickly problems regulating the internal temperature.

“When a human's internal temperature exceeds 40 ^oC, there can be damage to the organs if it lasts too long,” explains the D^r Javaid. The researcher published a study on normal human body temperature in 2019 in the journal Open Forum Infectious Diseases.

For internal temperature, we must distinguish between what is created by the response of the immune system and the body's reaction to a high external temperature. “When there is an infection, the human body's immune response increases the temperature, for reasons that are poorly understood,” says the New York researcher. The most I've seen in these situations is 107 ^oF [41,7 ^oC]. »

An American study, published in 1982 in the academic journal Annals of Emergency Medicinereports a temperature of 46.5 ^oC like the absolute record recorded in a human, according to the D^r Javaid. It involved a 52-year-old man who had spent the day cooking while drinking vodka during a heat wave in Atlanta. He arrived in the emergency room in a coma and had to be treated for three weeks for damage to his organs, but had no after-effects.

This would be an internal temperature record, according to the D^r Javaid. “He was lucky not to have any permanent damage. »

Fever

Uncertainty about the causes of the rise in temperature – fever – caused by the immune system's fight against infections is the scientific question with the most practical impact.

He specifies that the debate does not concern children, pregnant women and certain patients with chronic illnesses, for whom fever is more dangerous, and that everyone agrees that a fever that is too high or persistent must be treated. .

The Mount Sinai epidemiologist sent to The Press a 2024 study of theAmerican Journal of the Medical Sciences which reports on the fever debate. In mid-December, in the magazine PNASChinese researchers reported that tilapia swim to warmer waters when they have an infection.

The other clinically important aspect is the estimation of the “normal” human body temperature, which is the focus of the 2019 study by Dr.^r Javanese. The normal temperature, 37 ^oC, was established in the middle of the 19th^e century by the German doctor and psychiatrist Carl Wunderlich. Now it is considered 36.8 ^oC.

“We realize that there is more variability between individuals than we thought for this normal temperature,” says Dr.^r Javaid. The older we get, the more our normal temperature decreases, for reasons that are still poorly understood. This is why older people often feel cold. And there is a difference between the different methods of taking temperature, rectal, oral, ears, among others. »

And between men and women? There is very little difference, according to the D^r Javaid.

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