Fever and immunological reactions

An increase in body temperature is closely related to the activity of the immune system.

If a large number of pathogens penetrate the body this causes a disturbance. In response, the activity of certain parts of the immune system will increase. The immune system will secrete chemical messengers into the bloodstream, which then travel to the brain’s heat center stimulating an adjustment of the temperature „set point” (previously 37°C/98.6°F).

In other words, there is a perfectly-controlled loop between the immune system, the nervous system and heat production.

Many of the body’s important immune defense mechanisms are only activated by fever. Fever stimulates the activity of certain immune cells in the immune system (11, 148). In this way it also stops the proliferation of pathogens. In cases of serious infection the survival rate shows a close correlation to development of fever (12-14, 55, 86, 150). An increase in body temperature of as little as 1-4°C helps fight many infections (149).

At the same time, fever protects the body's own cells from the protective antibodies released by the immune cells. 

Meanwhile, the body protects its own (more heat-sensitive) proteins, called heat shock proteins, from the potential adverse effects of warming (148).

In this way, the body strikes an optimal balance between the benefits and drawbacks of fever, with precision and control.


How does fever work?

When someone develops a fever, several parts of the immune system become more active:

  1. Direct thermal effects reduce the proliferation of pathogens (9).
  2. Increasing antibody production in the humoral immune system neutralizes and destroys pathogens more easily (10).
  3. Through activation of the cellular immune system (11, 148). The proliferation, maturation and activity of white blood cells are increased. Immune cells then move faster, more actively absorb invading viruses, bacteria, and their antibody production speeds up. They present faster the antigens to be destroyed and neutralized. Unnecessary materials and debris are transported faster to the lymphatic pathways and lymph nodes.
Immune cells work more efficiently at higher body temperatures in every respect.

If we inhibit or reduce fever, we also slow down these mechanisms.


However, if a child is allowed to develop optimum fever, it will also help the child's immune system to mature. Colds and infections will become less frequent and shorter.

Thus, in most cases, the use of antibiotics for common infections is not justified. It is an interesting experience that in those rare cases in which antibiotic use is necessary, it will be more effective if the patient is allowed to remain febrile. Fever thus increases the antibacterial effect of antibiotics (8-11).

Accordingly, inhibition of fever is disadvantageous. We have known for some time that the use of antipyretics in viral diseases may lead to an increase in complications (6). The same is true for unrecognized blood poisoning (bacteremia), an infection in which the bacteria in the bloodstream being to invade the organs of the body (10-14).

In feverish conditions, the body defends itself adequately. It also activates substances that protect its own functioning and the organs. These are collectively referred to as heat shock proteins. This protects the nervous system and the heart.

So, the body raises its temperature (up to 41 degrees Celsius) while protecting its own heat-sensitive parts (organs, enzymes, proteins).

Despite some common beliefs and misconceptions that one’s brain will boil, and one’s protein will precipitate, these are mere fictions. 

In an optimal fever-process, the fever is a useful, protective event.


You can find the corresponding numbered references here: References

Version update: 1 March 2024