Submitted by Dr. Chris Spooner

Intentionally elevating body temperature has been used to treat disease since the 18th century. Fever is part of our body's defense mechanism. When our bodies are fighting infections, our body temperature rises. Fever is the body’s natural response to illness and has been shown in animal studies, to improve survival rates and shorten the duration of the disease (Jiang 2000).

For heat to exert a therapeutic effect, pathogens (bacteria, viruses, or neoplastic tissues) need to be susceptible within temperature ranges that do not exert deleterious effects on normal tissues. The minimal temperature of the therapeutic window falls at the maximum of normal physiologic fever. An elevated body temperature, or fever (between 37.5 and 41°C), does have a beneficial effect on the outcome of infections, (Kluger,1986) has been conserved across evolution, and is present throughout the animal kingdom. In order to have a ubiquitous biological presence, fever must play a beneficial role since it extracts a high metabolic cost. (Kluger,1979)

The therapeutic value of heat can be divided into two parts. One value is the beneficial effect on the body, such as enhanced immune surveillance, including increased mobility and activity of white blood cells, (Nahas, 1971; Moore, 1987) stimulation of interferon production (Chang, 1991) (an anti-viral and anti-tumor protein), and activation of T lymphocytes. (Roberts, 1977)

The second aspect of the therapeutic effect of heat is the harmful effect on the invading agent. Most pathogenic bacteria are live within a normal physiologic range of 33-41°C. (Mackowiak 1981) When the temperature is elevated, the growth rate decreases, mobility is decreased, and the cell wall is damaged.(Marr, 1966) All of these factors result in an increased inability of the bacteria to prevent environmental insults.

Viruses also show sensitivity to environmental heat. Elevated temperatures result in a large decrease in the propagation of many types of viruses, such as poliovirus,(Lwoff, 1959) influenza virus, herpes simplex virus,(Richman,1979) rabies virus, (Bell, 1974)) and transmissible gastroenteritis virus.(Furuuchi, 1976)

Enzyme reactions occur at a quicker rate, and mobilization of the cellular immune system improves. Immune efficiency improves and, with everything ticking over faster, there is also accelerated tissue repair. To make the circulatory environment hostile to the bacteria and viruses, the body shifts from glucose metabolism to one based on lipolysis (fat burning) and proteolysis (protein burning). Reducing the amount of free glucose available in the circulation that can be used by the invading microorganisms helps hinder the disease process.

This immune response is further enhanced by the release of acute phase proteins by the liver. As TNF, IL-1 and IL-6 are released by monocytes into the circulation, this has the effect of stimulating the production of an array of proteins and other substances in response to these inflammatory mediators.

Acute phase proteins are used for energy and tissue repair and also have a beneficial effect of binding cations necessary for bacterial replication (McCance and Huether 2002). Cations are positively charged ions and are minerals such as iron, copper and zinc. The effect of binding these circulatory minerals reduces their circulatory concentration and ultimately limits their supply. These minerals are required for bacterial and viral reproduction; if they are not present in normal circulatory concentration the rate of pathogen replication is slowed down and so influencing the progression of the disease process (Montague et al 2005). As the fever continues, cellular autodestruction is used as a method of controlling the spread of infection.

An increasing body temperature directly affects the invading organisms. Most bacteria are heat sensitive and function most efficiently between 33ºC to 41ºC (Mackowiak 1981). As the temperature is elevated growth rate and mobility is decreased, selfdestruction of the bacteria (autolysis) increases and cell walls become damaged (Vertree et al 2002). Likewise, viruses are sensitive to environmental temperature and slow down their rate of replication.

The duration of the therapeutic thermal exposure ends when target tissue is either destroyed or protected from further thermal destruction, or normal tissue becomes threatened. A normal response of cells to thermal stress is the production of heat shock proteins (HSPs), which act as chaperones and have a protective effect on cellular ultrastructure, shielding essential proteins from thermal disruption. (Schlesinger,1986)

Sauna can mimic the effects of fever. In one study (Myhre 1977) Elevated body temperature caused by sauna caused white blood cell (leukocyte) and serum total protein levels to increase beyond what was predicted.

All white blood cells are known officially as leukocytes. White blood cells are not like normal cells in the body -- they actually act like independent, living single-cell organisms able to move and capture things on their own. White blood cells behave very much like amoeba in their movements and are able to engulf other cells and bacteria. Many white blood cells cannot divide and reproduce on their own, but instead have a factory somewhere in the body that produces them. That factory is the bone marrow.

Leukocytes are divided into three classes:

• Granulocytes - Granulocytes make up 50% to 60% of all leukocytes. Granulocytes are themselves divided into three classes: neutro phils, eosinophils and basophils. Granulocytes get their name because they contain granules, and these granules contain different chemicals depending on the type of cell.
• Lymphocyte - Lymphocytes make up 30% to 40% of all leukocytes. Lymphocytes come in two classes: B cells (those that mature in bone marrow) and T cells (those that mature in the thymus).
• Monocyte - Monocytes make up 7% or so of all leukocytes. Monocytes evolve into macro phages.

Another type of white blood cell, the Eosinophil, decreased significantly after sauna in the same study, while other leukocyte counts tended to increase. Eosinophils along with basophils and mast cells, are important mediators of allergic responses and asthma pathogenesis and are associated with disease severity. (Rothenberg, 2006; Shi, 2004)

The effect that raising the body temperature has on the immune system suggests that sauna may have the potential to help fight infection and improve immune function. The improved immune function that occurs with the activation of white blood cells and increases in important immune signals and proteins, in addition to the direct effect of elevated temperature on bacteria and viruses, make sauna a safe adjunctive therapy for infections and possibly allergies.