Fever: the knight of the immune system

A symptom to fight or an ally to understand?

Fever is probably one of the most feared and misunderstood symptoms. In common perception, it represents something to be eliminated as quickly as possible, often by immediately resorting to antipyretic drugs. In reality, from a biological and evolutionary point of view, fever constitutes one of the most sophisticated defense mechanisms developed by living organisms against infections.

Present in numerous animal species, from insects to mammals, the febrile response has been preserved throughout evolution because it offers a concrete advantage in the fight against viruses, bacteria, and other pathogens. Fever is therefore not a disease, but an adaptive response of the organism.

Why does our body produce fever?

When a virus or bacterium invades the organism, the immune system releases substances called pro-inflammatory cytokines, including interleukin-1 (IL-1), interleukin-6 (IL-6), and TNF-α. These mediators act on the hypothalamus, the brain center that regulates body temperature, inducing an increase in the thermal "set point".

The rise in temperature determines numerous favorable effects:

• increased activity of immune cells;
• greater antibody production;
• improved functioning of T lymphocytes;
• increased phagocytosis by macrophages and neutrophils;
• reduction in the replication of many viruses and bacteria;
• increased production of proteins involved in the immune response.

According to a review published by Evans and colleagues, fever represents a central element of the innate and adaptive immune response, improving the efficiency of the body's defense mechanisms.

Fever hinders viral replication

Many viruses replicate optimally at physiological temperatures. The increase in body temperature creates an environment less favorable to their proliferation.

Furthermore, the acute inflammation that accompanies fever induces metabolic and cellular changes that help limit the spread of the infection.

Experimental studies have shown that pharmacological suppression of the inflammatory response can, in some contexts, promote viral replication and worsen the progression of the infection.

It is not always necessary to lower a fever

In most common viral infections, fever represents a useful and physiological response.

The intensity of the fever does not necessarily coincide with the severity of the illness. Some people maintain good vitality even with high temperatures, while others may feel particularly exhausted with a mild fever.

For this reason, it is important to observe not only the numerical value of the temperature, but also:

• general state;
• hydration level;
• ability to eat;
• presence of neurological symptoms;
• any pre-existing conditions.

In healthy individuals, a short-lived fever, even a high one, is generally well tolerated.

Of course, there are situations that require prompt medical evaluation, such as:

• meningitis;
• severe pneumonia;
• sepsis;
• severe dehydration;
• breathing difficulties;
• febrile convulsions;
• persistent or unexplained fever.

What do we know about antipyretic drugs?

Paracetamol and nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used to reduce fever and relieve discomfort.

However, some evidence suggests that systematically reducing fever may not always be beneficial.

A randomized study on childhood chickenpox observed a slight prolongation of the illness in children treated with paracetamol. Other experimental studies have shown a less efficient immune response in individuals with viral infections treated early with antipyretics.

This does not mean that such drugs should be avoided altogether, but that their use should be guided by clinical assessment and the patient's well-being, not exclusively by the temperature reading.

It should also be remembered that chronic and high-dose use of paracetamol can be associated with cardiovascular, gastrointestinal, and renal side effects.

Cough, mucus, and diarrhea are also defense mechanisms

Fever is not the only protective mechanism.

The body uses several strategies to eliminate infectious agents:

• coughing helps expel secretions;
• mucus traps microorganisms and particles;
• diarrhea accelerates the elimination of intestinal pathogens;
• vomiting protects against toxic substances;
• reduced appetite temporarily limits the supply of nutrients usable by pathogens.

In many cases, these symptoms represent biological responses aimed at recovery.

Antibiotics: useless against viruses

One of the most widespread misconceptions is that antibiotics can speed up recovery from viral infections.

Antibiotics act exclusively against bacteria and have no effect against viruses responsible for colds, influenza, many cases of pharyngitis, and numerous acute respiratory syndromes.

Inappropriate use of antibiotics leads to:

• alterations in the intestinal microbiota;
• increased bacterial resistance;
• a greater risk of side effects.

For this reason, major international guidelines recommend the prudent and appropriate use of these medications.

How to support the body during a fever

During a febrile episode, it is important to support the body's natural recovery processes.

The main recommendations include:

Adequate rest

Sleep and rest allow the immune system to focus its energy on recovery processes.

Hydration

Fever increases fluid loss through sweating and breathing. It is therefore essential to drink water regularly and, if necessary, rehydration solutions.

Light diet

Fresh fruit and vegetables provide vitamins, minerals, polyphenols, and other antioxidants that are useful during the inflammatory phase.

Keeping the body warm

According to naturopathic tradition and clinical observation, keeping the feet and legs warm can help make the patient more comfortable during febrile episodes, preventing the cold sensations and chills that increase energy expenditure.

Phytotherapy support

Some medicinal plants have traditionally been used to support the body's defenses.

Echinacea

Numerous studies have evaluated the role of echinacea in immune support, highlighting immunomodulating effects and a possible reduction in the duration of some respiratory infections.

Eleuthero

Considered an adaptogen, it can help maintain the body's resistance to physical and biological stress.

Vitamin C, vitamin D, and trace elements

Vitamin C, vitamin D, zinc, copper, manganese, and selenium play essential roles in the immune response and protection against oxidative stress.

White willow: the natural precursor to aspirin

White willow (Salix alba) contains salicin, a substance that is converted into salicylic acid in the body.

Its traditional properties include:

• antipyretic activity;
• anti-inflammatory action;
• analgesic effect.

The discovery of salicylic acid came from studies on willow bark, which inspired the development of acetylsalicylic acid (aspirin).

Eucalyptus: an ally for the respiratory tract

Eucalyptus essential oil (Eucalyptus globulus) is particularly rich in eucalyptol (1,8-cineole), a substance with:

• balsamic;
• fluidifying;
• expectorant;
• antimicrobial properties.

Steam inhalation and environmental diffusion can help improve respiratory comfort in cases of colds, nasal congestion, and sinusitis.

Topical use of diluted essential oil also produces a cooling sensation that can be pleasant during febrile states.

Conclusions

Fever represents one of the body's most important defense mechanisms. In most uncomplicated acute infections, it aids the immune system and helps limit the replication of pathogens.

Rather than being automatically suppressed, fever should be interpreted within the context of the person's overall clinical condition. Rest, hydration, adequate nutrition, and support of the body's natural immune defenses are often the most appropriate strategies to aid the healing process.

Naturally, in the presence of severe symptoms, persistent fever, or particular clinical conditions, it is essential to seek medical attention promptly.

Clinical note: fever in young children, frail elderly people, immunocompromised patients, or in the presence of severe symptoms always requires an individual medical assessment. Some claims reported in naturopathic literature regarding the systematic use of antipyretics and antidiarrheals are not supported by all modern medical guidelines and should be interpreted within the context of the individual patient.

Essential bibliography

1. Evans SS, Repasky EA, Fisher DT. Fever and the thermal regulation of immunity. Nature Reviews Immunology. 2015;15(6):335-349.
2. Graham NMH, Burrell CJ, Douglas RM, Debelle P, Davies L. Adverse effects of aspirin, acetaminophen, and ibuprofen on immune function and viral shedding. Journal of Infectious Diseases. 1990;162(6):1277-1282.
3. Doran TF, De Angelis C, Baumgardner RA, Mellits ED. Acetaminophen: more harm than good for chickenpox? Journal of Pediatrics. 1989;114(6):1045-1048.
4. Roberts E, Delgado Nunes V, Buckner S, et al. Paracetamol: not as safe as we thought? A systematic literature review. Annals of the Rheumatic Diseases. 2016;75(3):552-559.
5. McCrae JC, Morrison EE, MacIntyre IM, Dear JW, Webb DJ. Long-term adverse effects of paracetamol. British Journal of Clinical Pharmacology. 2018;84(10):2218-2230.
6. Bauer AZ, Kriebel D, Herbert MR, Bornehag CG, Swan SH. Prenatal paracetamol exposure and child neurodevelopment. Hormones and Behavior. 2018;101:125-147.
7. Ranasinghe P, Pigera S, Premakumara GAS, et al. Medicinal properties of Salix species: a systematic review. Complementary Therapies in Medicine. 2013;21(1):26-34.
8. Juergens UR. Anti-inflammatory properties of 1,8-cineole (eucalyptol). Respiratory Medicine. 2014;108(1):27-35.