Now, perhaps more so than any other time in our recent past, the global community views health as the ultimate wealth. As the pandemic takes hold, we understand now more acutely than ever before how important it is to protect and maximise our health. While there is a myriad of ways to increase the body’s ability to protect itself from illness, this article will focus on the natural way that raised body temperature is the automatic response of the human species, and other vertebrates, to fight viral and bacterial infections, and quite literally boost the immune system. This blog will also attempt to examine the similarities between naturally induced fever, and artificially raising body temperature through routine sauna use.

The healing power of artificially induced fever has been well documented throughout human history. In ancient Egypt, Greece, the Roman and Persian Empires, as well as the first half of the 19th century, fever therapy was utilised for its healing effects. Fever therapy, or Pyrotherapy, has been used to treat infection in the body, and has also been used in conjunction with vaccination, with positive outcomes, by Nobel Prize winner, Wagner-Jauregg.

Daniel M. Davis writes, in his book The Beautiful Cure: The New Science of Human Health, ‘Raising temperature helps the body fight infections in all kinds of ways, affecting germs directly and increasing the activity of the immune system. Most germs that afflict us have evolved to thrive at normal body temperature. As a result, the replication rate of a virus, for example, decreases 200-fold when the temperature is increased to 40-41°C. A fever also helps the immune system by increasing the number of immune cells entering the bloodstream from bone marrow, where they are produced. As a result of this, and because heat also causes immune cells to make receptor proteins which direct them to sites of inflammation, a fever increases the flow of immune cells to where they’re needed.’

In a series of ground-braking experiments in the mid-1970s, Matthew Kluger, a scientist in the Department of Physiology at the University of Michigan, demonstrated that animals prohibited from developing a fever were more likely to suffer or die from infection. Kluger infected lizards with a bacterium called Aeromonas hydrophila, and then he put the lizards in chambers at 38°C (normal lizard temperature), 40°C (low fever), and 42°C (high fever). At normal temperature 75% of the lizards died, at low fever 33% of the lizards died, and at high fever no lizards died. These findings were later extended to goldfish infected with Aeromonas, mice infected with coxsackie B virus or Klebsiella, rabbits infected with Pasteurella, and dogs infected with herpes virus. In each set of experiments the findings were the same, fever improved the animals’ response to infection. Kluger concluded that fever was an adaptive, physiologic, necessary part of the immune response. With this finding in mind, is the way that saunas raise body temperature the reason why we are seeing such a wide range of health benefits from routine sauna bathing, and can saunas help the body to fight off infection, or even help prevent infection from taking hold?

The most common cause of fever in the UK is viral infection. Saunas raise body temperature, having a very similar effect on the body as fever. Raising body temperature helps to activate the immune system by altering surface proteins on immune cells, like lymphocytes, to make them better able to travel via blood vessels to reach the site of infection. When we routinely partake in sauna use, and raise our body temperature, it is not unreasonable to assume that the rise in body temperature is likely to result in the same activation of immune cells, as this is what science has proven fever to do. With this effect in mind, saunas may serve to rejuvenate the body, and may be in part the reason why we witness so many health benefits from regular sauna bathing. There are many anecdotal accounts of individuals observing positive effects on their immune systems after partaking in a period of sauna use, and science is now starting to catch up with the evidence to support existing assumptions.

In the modern Western world, we typically equate fever with illness, and as such automatically attempt to treat the fever under the assumption that we are treating the illness. However, as we have seen, this is a fundamental mistake. Fever is not an illness; it is the body’s natural response to illness. When we automatically assume that by reducing body temperature, we are aiding the recovery process, what we are actually doing is hampering the body’s natural ability to fight infection. Raising body temperature is one of the fundamental ways in which the body naturally boosts the immune system, because the thermal element of fever stimulates innate and adaptive immune responses, meaning that increased body temperature is a way of the body communicating with immune cells, instructing them to behave accordingly to the threat posed by viral and bacterial infections. There is evidence to suggest that this also works in the case of pain and inflammation.

Sharon S. Evans, Elizabeth A. Repasky, and Daniel T. Fisher, in their article on fever and the thermal regulation of immunity, write, ‘Fever is a cardinal response to infection that has been conserved in warm and cold-blooded vertebrates for over 600 million years of evolution. The fever response is executed by integrated physiological and neuronal circuitry and confers a survival benefit during infection.’

So, what if we can in effect high jack the way in which the body has evolved to create a rise in body temperature in order to boost the immune system, effectively activating the immune system on will, and more frequently. Over the course of millions of years, vertebrates have survived and continued to evolve in part due to their relationship with raised body temperature during periods of infection. Even cold-blooded animals move to areas where they can more drastically raise their body temperature when they are suffering from an infection; and this is effectively what we humans are doing every time we use saunas.

To naturally create a fever requires energy, and in times when food was scarce, routinely raising body temperature in the absence of infection was not the most effective use of precious calories. When infection is detected in the body, the hypothalamus signals for the production of noradrenaline, which in turn constricts blood vessels in the body’s extremities, triggering the body to begin burning energy from brown fat cells to produce heat. Acetylcholine acts on the muscles to cause shivering, which also serves to increase body temperature, but again this is an involuntary process and must be chemically triggered within the body.

The way in which these processes require the burning of calories means that the human body only raises its temperature when it is absolutely necessary, in a sort of two-fold survival strategy. However, human ingenuity has not only managed to stabilise food sources through agriculture, but it has also found ways of artificially raising body temperature, to take advantage of a natural immune boosting process, through saunas. Saunas raise the internal body temperature just enough to artificially recreate the internal body temperature that we see during fever, but not enough to cause harm to the body. Sauna bathing is the most effective way of artificially raising body temperature, and has been used by the human race for thousands of years. Saunas can be seen as a way of bypassing the chemical communication required within the body to raise body temperature, and thus inciting the subsequent immune boosting potential of fever, or raised body temperature, also known as pyrotherapy.

The immune response is an intricate system that has facilitated the existence of complex life for hundreds of millions of years. In the interest of human health and well-being, we should seek to support and enhance the immune system by studying it and understanding how it operates, so that we can in turn apply that knowledge to enhancing a process that has been refined over such a fantastically long period of time. Sauna Bathing works with the body, in such a way that it negates the harmful side effects that come hand in hand with pharmacological treatments. Saunas capitalises on the way in which our bodies naturally provide the building blocks for health and longevity, working with the immune system, enhancing an already sophisticated network of defence processes within the body. So, sit back, relax, and let your sauna do the work.