An elevated body temperature is a common symptom of illness. In adults, a body temperature of 38 C or higher is, by definition, considered a fever (pyrexia). Find out what you can do about a fever, how dangerous it really is and when you need medical treatment.
Overview
In general, a fever is the body’s defence mechanism. A fever is therefore not a disease itself, but rather the body’s response to a variety of factor. Amongst other things, it is a clear sign that the body is fighting off infections.
Fever is a common occurrence throughout life and is usually nothing to worry about. However, special caution is advised if it is particularly high, lasts for a long time or occurs in any of the following groups.
The symptoms of a fever should not be taken lightly in babies, young children, the elderly, cancer patients or people with a weakened immune system. If high-risk groups develop a fever, they should see a doctor as soon as possible.
In these groups, a fever can be an important indication of a serious or rapidly progressing infection and can quickly develop into a dangerous condition, as the body’s immune system is often compromised and typical warning signs may be less pronounced.
Inflammatory response
Fever is very common with inflammation. In response, the body releases fever-inducing substances (pyrogens) which send a signal to the hypothalamus, causing the body temperature to rise.
Fighting infection
Fever increases the activity of certain immune cells such as white blood cells. These help fight off pathogens. In addition, an elevated body temperature prevents pathogens from multiplying rapidly: high body temperatures are unfavourable for many viruses and bacteria.
Supporting healing processes
Certain biochemical processes in the body that contribute to healing, such as tissue repair, are accelerated by a higher body temperature.
Response to illness, injury or stress
In addition to infections, many other conditions can also lead to fever, including:
- Cancer
- Autoimmune diseases
- Heat accumulation (hyperthermia)
- Metabolic disorders
External influences
A number of external influences can also cause a fever:
- Exposure to contaminants or toxic substances
- Allergic reactions, especially to insect bites and medications
- Side effects of medication (drug-induced fever)
- Stress
When should you see a doctor if you have a fever?
Although a fever is usually harmless, special caution is advised if accompanying symptoms develop or if the fever is persistent or high. In such cases, it is important to seek medical advice promptly. You should seek immediate medical attention for a fever if you experience one or more of the following symptoms:
- A temperature above 40 C
- Persistent mild fever lasting for weeks
- Severe vomiting
- Severe diarrhoea
- Drowsiness
- Confusion
- Palpitations or shortness of breath
- Failure to pass urine
- Unexplained skin rashes or joint swelling
- Severe headaches or a stiff neck
- Febrile seizures (characterised by loss of consciousness, especially in young children)
- Taking medications that suppress the immune system (immunosuppressants)
Important to note: a fever in babies or people with weakened immune systems, as well as a fever following travel to tropical countries, should always be investigated immediately. It should also be noted that the severity of a fever does not always indicate the severity of an illness. Accompanying symptoms therefore play a key role in the assessment of an illness.
How long can a fever last?
Fever in babies: in the event of a fever in babies up to three months of age, a paediatrician should be consulted immediately as a precaution to investigate the cause.
Fever in young children: in the event of a fever in young children between three months and two years, they should be seen by a doctor if the fever lasts for more than one day.
Fever in children (>2 years) and adults: if none of the accompanying symptoms listed above occur and the general condition of older children (> 2 years) and adults is not significantly impaired, a doctor should be consulted if the fever persists for more than three to four days. In addition, a medical examination is advised if those affected are no longer able to drink enough fluids or feel very exhausted.
When do you have a fever?
Fever in adults: a normal body temperature is between 36.5 C and 37.4°C
A temperature between 37.5°C and 38.0°C is considered to be a raised temperature. In adults, a body temperature of over 38.0 C is considered to be a fever. A temperature of over 39°C is classified as a high fever and 40°C or above is classified as a very high fever (hyperpyrexia).
Fever in children: in children, a temperature of up to 38.4°C is considered to be raised. A temperature of 38.5 C or higher is considered to be a fever.
Fever in babies: in infants under three months of age, a temperature of 38°C or above is considered to be a fever. Infants under three months of age should be examined by a doctor immediately if they have a fever.
How do you take a temperature correctly?
Body temperature can be taken in the ear, under the tongue, in the armpit, on the forehead or rectally. Depending on the chosen location, the temperature is measured using a digital thermometer, an expansion thermometer, an ear thermometer or a forehead thermometer.
Digital thermometers
Digital thermometers are considered to be the most reliable and practical way to take a temperature. Rectal measurements (taken in the bottom) and ear measurements are particularly accurate. The temperature is taken within 30 to 60 seconds and then displayed.
Expansion thermometers
Expansion thermometers are also very reliable, although reading the scale requires some practice. Inside these thermometers is a coloured liquid that expands when exposed to body heat. A reading takes about five minutes.
Ear thermometers
Ear thermometers measure the heat radiation from the eardrum using an infrared sensor. They provide a reading within seconds and ensure a quick and straightforward measurement. Ear thermometers should not be used in cases of middle ear infection.
Forehead thermometers
Forehead thermometers measure the temperature on the forehead or temple via infrared. They are particularly comfortable to use. However, the readings may be less accurate than with other methods, especially with non-contact devices.
Treatment
Since fever is part of the immune system, it does not always have to be lowered. If the temperature reaches 39°C or above, measures to reduce fever are generally recommended. For people with underlying health conditions, children and those who find a fever particularly distressing, appropriate measures can be taken even at when body temperature is lower. Fever can be brought down by medication but also by home remedies.
Medication to reduce fever
Tried-and-tested medication to reduce fever include ibuprofen and paracetamol. The great advantage of these active substances is that they can also alleviate accompanying symptoms such as aching limbs and headaches.
Home remedies for fever
In addition to medication, tried-and-tested home remedies can also be used to lower body temperature. The following home remedies can help:
- Drinking plenty of fluids: sufficient hydration in the form of tea and water helps to counteract fluid loss caused by increased sweating. Diluted juices and broth can also be helpful. Linden tea, ginger tea or a glass of water with a little honey and two tablespoons of apple cider vinegar can also reduce fever.
- Getting bed rest (in a cooler room with dim lighting): resting in bed and rest in general allow the body to regenerate efficiently. It is recommended to avoid strenuous activities and get enough sleep to recover.
- Taking a lukewarm bath: if the temperature is only slightly elevated, lukewarm baths can help bring a fever down. However, hot baths should be avoided, as they can put a strain on the body and circulation, and can cause the body temperature to rise even further.
- Using calf compresses: calves compress gently lower body temperature. To do this, dip two tea towels or hand towels into a litre of lukewarm water with two tablespoons of vinegar or lemon juice, wring them out and place them on the calves. Then, wrap dry towels around each calf and rest in bed for 15 minutes. Calf compresses should only be used if the person’s feet and legs are warm. If the temperature does not drop
Prevention
Since fever is not a disease in itself but a reaction to infections and other stress factors, prevention is mainly through indirect means, for example, by strengthening the immune system and preventing infections. This includes washing hands regularly and thoroughly, especially after contact with many people or before eating, as well as avoiding close contact with sick people.
A balanced diet, adequate sleep and regular exercise also support the body’s own immune system. Vaccinations can also help prevent certain infectious diseases and, as a result, often the fever that accompanies them.
How long should you stay at home if you have a fever?
If you have a fever, you should stay at home until your temperature has returned to normal for at least 24 hours without needing to take fever-reducing medicine. Resting at home promotes recovery without the risk of exposing others to an infection (depending on the underlying illness).
How often should you take your temperature if you have a fever?
If you have a fever, it’s advisable to take your temperature two to three times a day to keep an eye on how your temperature progresses. If you have taken medication, you should wait 30 to 60 minutes before taking your temperature.
Why do you get chills when you have a fever?
Chills occur because the body increases its target body temperature in order to fight off pathogens. Muscle tremors generate additional heat, which allows the body to reach the new target temperature more quickly. Once this target temperature is reached, any chills will subside.