Last Updated on August 19, 2023
Fever is a condition where the body temperature goes above the normal range. The normal range is 36–37° Centigrade or 98–100° Fahrenheit).
It is a very common symptom occurring due to infection, inflammation or other body conditions releasing pyrogens.
Pyrexia is another term for it.
Body’s core temperature is controlled by anterior hypothalamus. Pyrogens released in the body set this core temperature to a higher level and cause body temperature to rise [similar to raising the temperature on the thermostat.]
This is in contrast to hyperthermia where the body temperature rises without a change in the heat control centers.
The rise in temperature of the body causes an unpleasant sensation.
How does Fever Occur?
The body temperature refers to the temperature of the viscera and tissues of the body. It is kept within the normal level by maintaining a balance between heat gain and heat loss, which is regulated by the hypothalamus.
Normal body temperature is affected by various factors like diet, exercise, and sleep.
There is a diurnal variation in the temperature too. The temperature is highest in the evening and lowest in late night/early morning hours.
A rise in body temperature is body’s defence against infections and other insults carried out by the release of pyrogens which act on the temperature regulation centers. It helps in curbing bacteriae or virus.
But a very high rise in temperature can be dangerous and lead to complications.
In fact, it is not recommended to bring mild fevers down in case of infections. But a high fever needs to be controlled with antipyretic drugs and other measures.
Fever or pyrexia is an increase of more than 1 degree Celsius or any rise above the maximal normal temperature.
Associated Symptoms
Fever itself is a symptom but when it occurs, there are other symptoms that one may feel.
Not all patients feel all the symptoms.
- feeling cold with or without shivering
- decrease in appetite
- lethargy
- tiredness
- sleepiness
- sweating
A high temperature can cause irritability, confusion, delirium, and seizures.
Classification
- mild, from or 38.1–39°C
- moderate, from or 39.1–40°C
- high, from to or 40.1-41.1°C
- hyperpyrexia, above 106.0°F or 41.1°C
A fever lasting less than 7 days is called acute, <14 days subacute, and chronic if occurs for more than 14 days.
How to Measure Temperature
Body temperature can be measured by a thermometer. There are various types of thermometers that can be used for the measurement of temperature. Oral cavity and armpits are the places where most thermometers are used.
The body temperature is best recorded with a mercury thermometer which should be kept in position for about a minute. Usually, the temperature is recorded in the axilla.
The digital thermometer is a safe and commonly used device to record the temperature. Oral temperature is taken b placing the tip under the tongue. Armpit is another place that can be used to take the temperature. Armpit temperature is generally half to one degree lower than oral temperature.
Causes of Fever
Fever may occur whenever pyrogens are released into the body. This may occur in
- Infection
- Bacterial
- Viral
- Other like rickettsial, fungal or parasitic.
- Tumors
- Hypernephroma
- Lymphoproliferative malignancies
- Carcinoma of pancreas
- Hepatoma
- Vascular Causes
- Acute myocardial infarction
- Pulmonary embolism
- Pontine hemorrhage may also cause fever.
- Trauma like a massive crush injury
- Immunological Diseases
- Endocrine diseases like thyrotoxicosis and Addison’s disease
- Metabolic diseases like Gout, porphyria etc
- Sunburns
Home Treatment Vs Seeing A Physician
Most of the time fevers are mild and have seasonal causes like flu. The conditions associated with the temperature would suggest the probable cause. A fever associated with a running nose, and cough would be mostly due to seasonal flu.
A physician need not be immediately seen if the fever is mild and is of recent onset. Moderate to high-grade fever may warrant seeing a physician immediately or urgently.
At home following measures may help
- Sponging
- Drugs like paracetamol
- Rest
Diagnosis
A raised body temperature can tell the presence of a fever. But the fever is a symptom, not an illness. Most of the time further probing is not necessary. But when required a workup for reaching the diagnosis may be done.
The workup may include blood and urine tests and or imaging.
Treatment
- Non-steroidal anti-inflammatory drugs are the medications given to bring the temperature down.
- Paracetamol is the most common antipyretic drug used. But it should be used with restraint especially in children.
- In fact, mild fever need not be brought down as it is beneficial for the body.
- In the case of bacterial infections, antibiotics may be prescribed.
- Plenty of fluid should be consumed as fever is a state of high temperature and the body loses a lot of water.
- Water sponging is done in as a supportive measure but is contraindicated in children.
Complications
Fever usually responds to medications or follows a self-limiting course. It induces a state of catabolism which is detrimental to the body. It may also lead to fluid and electrolyte imbalance due to sweating and loss of minerals. High-grade fevers can lead to convulsions, brain damage, circulatory overload, and arrhythmia.
A high temperature in children can lead to seizures.
Hyperpyrexia is said to occur when body temperature is more than 105 degrees Fahrenheit. It usually occurs in the following conditions
- Tetanus
- Malaria
- Septicemia
- Heat Stroke
- Encephalitis
- Pontine hemorrhage
References
- Garami A, Székely M. Body temperature: Its regulation in framework of energy balance. Temperature (Austin). 2014 May 6;1(1):28-9. doi: 10.4161/temp.29060.
- Blomqvist A, Engblom D. Neural Mechanisms of Inflammation-Induced Fever. Neuroscientist. 2018 Aug;24(4):381-399. doi: 10.1177/1073858418760481.
