Fever: Common Causes and Treatment

Fever is a sign that the body’s immune system is fighting against pathogens. We reveal causes and how to treat fever.

What is fever?

Fever describes a significantly increased body temperature from 38 degrees Celsius. However, contrary to what is often thought, fever is not a bad thing in itself – it is a normal protective reaction of the body, which fights off pathogens such as viruses and bacteria by heating up. The fever is often accompanied by symptoms such as dry skin and loss of appetite. In many cases, home remedies for fever can lower the high body temperature again, and some medications also have a fever-reducing effect.

Fever – The helper of the immune system

If pathogens such as viruses, bacteria or fungi penetrate the body, the immune system is activated. Many different substances are released in the process, including so-called pyrogens – they send a signal to the brain to raise the body temperature by heating it up, thus triggering fever. The same effect occurs, for example, in an existing autoimmune disease or when malignant tumors form.

What causes fever?

The body’s thermoregulatory center is located in the hypothalamus of the brain. When the body heats up, the blood vessels are dilated and we sweat more. If it is too cold, the blood vessels become narrower and we get goose bumps – the body should therefore lose less heat. At the same time the metabolism is stimulated and muscle trembling occurs. Both of these factors should result in the body producing more heat.

Even with fever, the blood vessels constrict so that the body does not lose heat but can use it to heat up. The skin becomes pale and cold, muscle trembling and even chills can occur. When the signal comes from the hypothalamus to lower the fever, the vessels dilate again – the skin becomes warm and red and we start to sweat in order to release the now superfluous heat.

When does my fever start?

Whether someone has an elevated body temperature or actually has a fever is determined. Thus the respective body temperature is defined:

• Slightly elevated temperature: 37.5 to 38 degrees Celsius
• Mild fever: 38 to 38.5 degrees Celsius
• Moderate fever: 38.6 to 39 degrees Celsius
• High fever: 39.1 to 39.9 degrees Celsius
• Very high fever: 40 to 40.9 degrees Celsius
• Extreme fever: 41 degrees Celsius and higher

Extreme fever is very dangerous – it can cause permanent damage to both organs and tissue. A body temperature above 42.6 degrees is normally considered fatal.

Taking a temperature: How to do it right

The temperature should always be measured at the same time and in the same way in order to obtain the most correct result. The measurement is most accurate when taken rectally. For oral measurement, about 0.3 to 05, degrees are added to the result. More information about this can be found in the article Taking a Temperature.

What causes can fever have?

There can be many different causes for fever. Common triggers are:

• Cold or flu
• Other infections, e.g. tonsillitis or blood poisoning
• Inflammation of renal pelvis
• Appendicitis
• Pneumonia
• Purulent abscesses
• Connective tissue diseases
• Tuberculosis
• Lymph gland cancer
• Chronic intestinal diseases, e.g. Crohn’s disease
• Rheumatic diseases, e.g. rheumatoid arthritis
• Hormonal Disorders
• Allergy
• Thromboses

It is not always possible to identify the cause of fever. One speaks of fever of unknown origin (FUO for short) if a patient has a body temperature of more than 38.3 degrees for more than three weeks for which there is no explanation. However, the triggers are often found much later – for example, previously undiscovered tumours or autoimmune diseases.

Fever in children

Children are also generally a special case: As their immune system is not yet fully developed, even small supposedly harmless infections can cause them to develop a fever. These include, for example, cold-related respiratory infections, gastrointestinal infections or middle ear infections. Infants are also a special case: in the case of serious infections, they sometimes do not develop a fever at all, which is why parents should pay attention to other signs of illness – for example listlessness, persistent vomiting or diarrhoea.

How does a fever run?

Without complications the fever usually runs in three phases:

• The fever rises up to a certain temperature
• The achieved temperature is maintained
• The fever drops and the body returns to its normal temperature

Depending on the cause, the process can take only a few hours, but often it can last several days.

Associated symptoms of fever

Fever does not usually come on its own: in most cases, other symptoms that indicate the fever occur. These include:

• Shining eyes
• Hot, dry skin
• Heavy sweating
• Strong feeling of illness, often with pain (especially limb and headaches)
• Severe thirst
• Rapid breathing
• Shivering up to chills
• Loss of appetite
• Sometimes diarrhea and / or vomiting
• Unrest
• Children: Whining

When should I see the doctor for fever?

In uncomplicated cases, where the fever is caused by a cold, for example, it usually disappears on its own within a few days. If the body temperature remains above 39.5 degrees for a long time or rises repeatedly, a doctor should be consulted. A visit to the doctor is also advisable in the following cases:

• Very strong feeling of illness
• Disturbances of consciousness occur
• Infant has a fever
• Children appear to be seriously ill

In general, increased caution is required with children – if the fever lasts longer than one day, if other symptoms occur or if the child is conspicuously listless, a prompt visit to the doctor is advisable.

Treatment: What helps against fever?

Fever does not have to be treated in every case, as it is part of the body’s defence reaction. But if it rises to 39 degrees, treatment is advisable. There are, for example, antipyretic drugs that can alleviate the additional pain that often occurs. Home remedies against fever also alleviate the symptoms:

• Calf compress: Our grandmother already used calf compresses to reduce fever – because calf compresses draw the excess heat out of the body. Simply wet cotton cloths with cold water, wrap them tightly around the calves and wrap two more layers of dry cloths around them. After five minutes, the calf compresses are removed and replaced two or three times if necessary. In this way the fever is slowly lowered. Caution: If you have chills, do not use calf compresses.
• Drink a lot: From a body temperature of 37 degrees Celsius, an additional 0.5 to one litre of water per day is recommended for every degree increase (normal daily amount is about two litres per day). Some of this can also be covered with herbal tea – elderberry blossom tea and lime blossom tea, for example, have a fever-reducing effect.
• Lukewarm bath: If you want to reduce fever, a lukewarm bath can help. To do this, fill the bathtub with warm water, then gradually add cold water until the temperature is around 25 degrees. After the bath, dry off well, wrap up warmly and put into bed.
• Bed rest: Speaking of bed: If you have a fever, it is advisable to stay in bed so that the body does not have to deal with the pathogens.