Among the many measures my locality is using to prevent the spread of Covid-19, temperatures are taken with a forehead scanner before people can enter the building. Curious to know how “hot” I was one cold, rainy day, I asked the attendant what it registered: 96.2.

The last time my temperature was checked in a medical setting it was 97.5. Whatever happened to 98.6° Fahrenheit that most doctors have long considered normal body temperature?

As if reading my mind, Dr Philippa Gordon, a Brooklyn paediatrician, sent me an article, “People’s Bodies Now Run Cooler Than ‘Normal’ — Even in the Bolivian Amazon”, by two anthropologists, Michael Gurven and Thomas Kraft, at the University of California, Santa Barbara, US.

As they wrote in The Conversation, a network of not-for-profit media outlets that publish online news stories written by academics and researchers, “There is no single universal ‘normal’ body temperature.” It varies not only from one person to another, but also over the course of the day — lower in the morning, higher in the evening; rising during and after exercise; varying at different times in the menstrual cycle, and at different ages — lower for old-timers like me.

Furthermore, researchers who took hundreds of thousands of temperature readings from people in Palo Alto, California, US, found that 97.5 was the new normal, down about a degree from what German physician Dr Carl Wunderlich established in 1867 in a study of 25,000 people.

In reviewing data from 1862 through 2017, Dr Julie Parsonnet, a professor at Stanford University School of Medicine, US, and her co-authors found a steady decline in average body temperature of about 0.05°F per decade. She has observed that at least 75 per cent of normal temperatures are now below 98.6.

If my body temperature registered 98.6, would that mean I have a fever? Possibly, said Sharon S. Evans, a professor of oncology and immunology at Roswell Park Comprehensive Cancer Center in Buffalo, New York, US, even though 100.4 is generally considered the lower end of the fever spectrum.

In a review written with two colleagues, Elizabeth A. Repasky and Daniel T. Fisher, Evans showed that under most circumstances, fever is beneficial, reducing the severity of illness and shortening its length.

“Fever acts to mobilise multiple arms on the immune system, a function that is remarkably well conserved across many, many species — both warm-blooded and cold-blooded,” she explained. “Fever affects every aspect of the immune system to make it work better.”

For starters, fever activates innate immunity — the mobilisation of white blood cells: neutrophils that patrol the body for pathogens and macrophages that gobble them up. Macrophages, in turn, send out an alarm that help is needed, prompting adaptive immunity — T cells and B cells — into action. These cells initiate a specific response to the invader: the production of antibodies days later.

“Treating fever can prolong or worsen illness,” Dr Paul Offit, vaccinologist at the University of Pennsylvania, US, stated in “Hippocrates Was Right: Treating Fever Is a Bad Idea,” a fascinating YouTube presentation by the College of Physicians of Philadelphia.

Thus, when you take medication such as acetaminophen or ibuprofen to suppress a fever, you actually work against the inherent protective benefits nature bestowed. Yes, a fever reducer would probably make you feel better, relieving symptoms such as headache, muscle aches and fatigue. But, Dr Offit emphasised: “You’re not supposed to feel better. You’re supposed to stay under the covers, keep warm and ride out the infection”, not go out and spread it to others.

Evans and colleagues wrote, “The fact that fever has been retained throughout vertebrate evolution strongly argues that febrile temperatures confer a survival advantage.”

So why are we so hellbent on suppressing fevers? Fear is one reason, said Dr Gordon, who said frantic parents often called in the middle of the night when a child’s fever spiked. She suggested that doctors warn parents to expect a nighttime rise in a child’s fever and explain that high fevers from an infection are not damaging.

“The body has a built-in thermostat — the hypothalamus — that keeps temperatures from getting high enough to cause damage,” she said, and febrile seizures (brief convulsions, shaking and perhaps loss of consciousness that affect some young children) result from how fast temperatures rise, not how high they get. In a genetically susceptible child, a seizure can occur when the temperature rises quickly even at low temperatures, say, from 99 to 100.8.

“Febrile seizures are creepy and terrifying for parents to watch, but they don’t cause any damage,” Gordon said. She added, however, that fever is worrisome in babies who have immature immune systems and haven’t yet been vaccinated against serious diseases.

Despite the infection-fighting benefits of fever, Dr Gordon said she would still recommend medication to lower a fever if a child, especially a nonverbal child, was very miserable and perhaps unable to sleep or eat. Adults should seek medical help if their fever rises above 103 degrees.

Consider how a temperature is taken before interpreting the results. An ear temperature is slightly higher than an oral temperature, which is higher than an armpit temperature or a forehead scan. The temperature of newborns should be taken with a rectal thermometer, Dr Gordon said. For older children, the exact number of degrees doesn’t really matter unless they’ve not been immunised, she said.

NYTNS