What is fever and how to reduce it? Why does it arise and what types does it have?

What is fever and how to reduce it? Why does it arise and what types does it have?
Photo source: Getty images

A fever is a rise in body temperature above 38 °C. It helps the body fight infection. When does it mean a problem?

Fever characteristics and body temperature values

Fever (pyrexia) is an increase in body temperature. It is a sign of ongoing disease. Fever may be fast or slow. It may be intermittent or constant.

The normal body temperature fluctuates by about 1 In most healthy people, it does not exceed 37 °C and does not fall below 35 °C. °C.

We speak of fever (febris) when the body temperature is above 38 °C.

A rise in body temperature between 37 and 38 °C is called subfebrile.

A body temperature above 40 °C is technically called hyperpyrexia.

Increases in temperature may be accompanied by shivering and chills. Muscle and joint pain, poor light tolerance, headaches or urinary disturbances are sometimes associated. Increased irritability and dehydration may be present.

Loss of appetite, general weakness and fatigue also occur.

There are several types of fever :

  • Continuous fever - the temperature does not fall below 38 °C.
  • Decreasing fever
  • Alternating fever - alternating between normal body temperature and higher values (even 39 °C)
  • Recurrent fever - alternating periods without fever with fevers
  • Relapsing fever - fluctuations in temperature of up to 2 °C during the day
  • Rolling fever - a gradual rise followed by a gradual fall in body temperature

Reaction of the organism

In the hypothalamus (part of the brain called the hypothalamus) there are centres for thermoregulation of fever. These centres evaluate information about body temperature. It is like a body thermostat. The centre is set at 36.5-37 °C.

At a lower blood flow temperature, the body immediately begins to prevent heat loss and increase heat production.

This results in:

  • constriction of blood vessels in the skin and subcutaneous tissue.
  • redistribution of blood from the periphery of the body to the internal organs
  • muscle tremors if necessary

If the flowing blood has a higher temperature(as in a fever):

  • dilation of blood vessels in the periphery
  • increased sweating
  • redistribution of blood from the internal organs to the periphery

There is an attempt to bring the body into a balanced "thermostat" state.

The change in the setting of the thermoregulatory centre is attributed to certain humoral substances, called pyrogens.

The pyrogens inhibit heat-sensitive neurons in the hypothalamus and excite cold-sensitive neurons. They maintain equilibrium. In some cases, however, a higher body temperature is necessary for the organism. This is especially the case in infectious diseases.

Fever - symptom
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The most common causes of fever are :

  • infections - viruses, bacteria, fungi, parasites
  • autoimmune and rheumatic diseases - systemic lupus erythematosus, rheumatic fever
  • damage to the thermoregulatory centre - in cancer, stroke, brain inflammation or degenerative diseases of the central nervous system
  • cancer - some cancers are accompanied by fever (leukaemia, lymphomas or metastatic tumours)
  • cardiovascular disease - pulmonary embolism, myocardial infarction
  • endocrine diseases - diseases of the endocrine glands
  • other diseases - haemolytic anaemia, sarcoidosis, Crohn's disease, etc.
  • heatstroke
  • certain vaccinations - diphtheria or tetanus vaccination
  • teething and tooth growth in children
  • food poisoning

Complications of fever

The main complications of pyrexia include:

  • dehydration - often associated with lower fluid intake
  • confusion - change in attention and concentration, inattention to surroundings
  • hallucinations - similarity to a waking dream, the patient may have visions and hear things that are not there
  • impaired breathing - deepened or shallow breathing, sometimes irregular
  • loss of consciousness - especially due to dehydration, patient may fall unconscious
  • convulsions - trembling of the limbs, general weakness as an accompanying complication of fever

Points of interest

Fever also has a protective function. The increase in body temperature leads to a reduction in the number of bacteria or other germs.

The increase in temperature activates the immune system.

An increase in body temperature impairs the survival of germs (bacteria, viruses, fungi, etc.). It activates the body's defence system.

Fever is therefore considered to be a helper in the fight against infection.

Sometimes fever can be a symptom of a serious illness.

For most adults and children, fever is unpleasant. But usually there is no need to worry.

Fever usually lasts for several days.

Various thermometers are used to measure fever - axillary, rectal, ear, oral. Oral and rectal (rectal) thermometers record the body core temperature.

In a young child (under 24 months), it is important to call for help if the rectal temperature is above 38°C.

In adults, a higher value, 38.9 °C, is considered dangerous. A rash, unusual sensitivity to light, headache, vomiting, etc. may occur.

The body temperature in the morning is usually slightly lower than in the afternoon and evening.

The body's struggle with infection can be unpleasant, but an elevated body temperature is desirable.

A complication of fever may be febrile convulsions, especially in children. They are seizures. They may be associated with loss of consciousness, trembling of the limbs on both sides of the body, rolling of the eyes, etc.

Some diseases are typical triggers of fever. These include malaria, Q fever, yellow fever, scarlet fever and dengue fever.

Fever is caused by many infections, most commonly by infections caused by bacteria and parasites.

Fever can also be caused by certain drugs such as cephalosporins or methyldopa. Fever has also been observed in users of psychostimulant drugs such as methamphetamine.

Diagnostic tests are sometimes necessary. White blood cell counts and urine counts or the presence of bacteria are evaluated. In some cases (suspected meningitis), a sample of cerebrospinal fluid (CSF) must be taken.

The menstrual cycle (ovulation) or intense exercise can lead to changes in body temperature and fever.

Not everyone has the same thermoregulatory load. People with slower metabolisms produce heat more slowly even under normal conditions during some exothermic reactions.

Fever - thermometer
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The best prevention of infectious diseases associated with fever is vaccination (inoculation) and adherence to epidemiological measures.

In some cases, it is advisable to wear a drape.

Good physical hygiene and hand hygiene are also important. It is also necessary to take proper care of the nasal area using sanitary napkins.


It is best to treat the disease itself. Symptomatic treatment is also given. This is treatment of the symptoms of the disease. Antipyretics such as paracetamol or acetylsalicylic acid are used. These reduce the body temperature for about 4 hours.

Read also the article:
Wrap helps reduce fever: or how to reduce fever without drugs

Intake of plenty of fluids and bed rest is recommended.

Cold packs or showering in cold water are also used.

The drug of choice may be corticosteroids to reduce fever.

Animation of a woman taking her temperature with a thermometer
Photo source: Getty Images
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