Understanding the Causes of Fever

9 September, 2025 Doctor Pediatrician 1 category

When the body’s temperature rises in response to an infection, it is called a fever. Hyperthermia, on the other hand, is an elevated body temperature not caused by a change in the body’s internal temperature regulation.

The body’s temperature can fluctuate throughout the day, reaching its lowest point in the early morning and its highest in the late afternoon. Fevers can vary in intensity and may come and go intermittently.

Temperature readings can be taken from different parts of the body, with the mouth and rectum being the most common sites. Depending on where the temperature is measured, certain readings are considered elevated and indicative of a fever.

Many individuals casually use the term “fever” without actually taking their temperature.

Factors such as age, overall health, occupation, and alcohol consumption can influence the body’s ability to develop a fever.

Symptoms and Effects of Fever

Fever symptoms are typically a result of the underlying cause of the fever, rather than the fever itself.

While fever serves as a defense mechanism against infections, extreme temperatures can be harmful, particularly to certain vulnerable individuals.

For adults with heart or lung conditions, a moderate fever can be risky, and it may worsen cognitive function in individuals with dementia.

In healthy children, fever can trigger febrile seizures.

Some common pyrogens that can trigger fever include bacterial and viral infections, as well as inflammatory conditions such as rheumatoid arthritis and inflammatory bowel disease. Additionally, certain medications, toxins, and allergens can also induce fever as a side effect.

It is important to identify the underlying cause of fever in order to properly treat the condition. In some cases, fever may be a normal response to an infection or inflammation, while in other cases it may indicate a more serious medical issue that requires immediate attention.

Causes of Fever

Infections caused by bacteria, viruses, or fungi are the primary reasons for fevers to develop.

Both upper and lower respiratory tract infections are frequent sources of infectious fevers.

Other common causes of fever include:

Urinary tract infections
Gastrointestinal infections
Skin infections
Ear infections
Flu or cold viruses
Medications or vaccines

It’s important to monitor your symptoms and seek medical attention if your fever persists or is accompanied by severe symptoms.

In addition to leukemia, lymphoma, and kidney cancer, other types of cancers such as liver cancer and pancreatic cancer can also cause fever as a symptom. It is important for individuals with unexplained persistent fever to seek medical attention to rule out underlying cancer.

Similarly, autoimmune inflammatory disorders such as Crohn’s disease and systemic lupus erythematosus (SLE) can lead to fever as a result of the body’s immune response attacking its own tissues. Managing these conditions with appropriate medication and lifestyle changes can help reduce fever episodes and improve overall quality of life.

Factors Influencing Diagnosis of Fever

Doctors consider various factors such as health status, age, occupation, medications, and exposure to infections when determining the likely cause of a fever.

Travel to regions with endemic diseases and certain medications or illicit substances can pose a risk for developing a fever.

Diagnosing and Treating Fever

Healthcare providers can often identify the presence of an infection through a brief medical history, physical examination, and basic tests.

Individuals exhibiting warning signs alongside a fever, such as changes in mental state or petechiae, should seek immediate medical attention.

When to Seek Medical Help for Fever

If warning signs are present, urgent medical attention should be sought, whereas individuals without warning signs should consider seeing a healthcare professional if the fever persists for more than 24 to 48 hours.

Initial Assessment of Fever

Initial inquiries by doctors typically focus on symptoms and medical history, followed by a physical examination to identify the potential cause of the fever and any necessary diagnostic procedures.

The presence of a fever does not always provide a clear diagnosis, but specific fever patterns may indicate certain conditions, such as recurring fevers every second or third day suggesting malaria.

Travel history is crucial, as it can offer insights into potential causes of fever, especially if the person has been to regions where specific infections are prevalent. Recent exposures, like working in certain environments, can also increase infection risks.

Pain localization and accompanying symptoms like cough, nasal congestion, or urinary issues aid in determining the underlying cause of the fever.

Additionally, inquiries regarding contact with infected individuals, pre-existing conditions, immunocompromised status, medications, and substance use help doctors in their assessment. Physical examinations start by confirming the presence of fever, with the necessity of further testing based on the history and findings from the examination.

While individuals with viral illnesses may not always require testing, exceptions exist for those exposed to particular diseases or in areas of high COVID-19 transmission. If a specific disorder is suspected, diagnostic tests may be recommended, especially for high-risk individuals, the elderly, or those who are severely ill.

Fevers are a natural response to infections, often accompanied by symptoms like sweating, chills, muscle aches, and temperatures above 38°C. Seek medical attention if the fever is persistent, with severe symptoms like intense headache or breathing difficulties.

If a fever lasts for more than three days without improvement, medical advice should be sought. Prompt consultation is also recommended for fevers with concerning symptoms, recent hospitalizations or travel, particularly for adults with severe symptoms or children showing signs of distress or dehydration.

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How is fever treated?

Self-care at home

If experiencing a high temperature, follow these guidelines to manage your condition. In case of persistent fever or concerns, consult a healthcare professional.

Stay hydrated

Keep yourself hydrated by consuming clear, non-alcoholic fluids.

Keep cool

Wear light clothing, maintain a comfortable room temperature, and avoid heavy bedding. Steer clear of cold baths or sponging as they may exacerbate discomfort.

Rest and refrain from strenuous activities when dealing with a fever.

Medicines for fever

Only take fever medications if you are feeling uncomfortable. Consider pain relief medications if necessary and consult with a healthcare provider before taking any medication.

Consider your medical conditions
Check for interactions with other medications
Consult if you are pregnant or breastfeeding

Can fevers be prevented?

Fevers are a natural immune response, but seek medical attention if the fever persists or if new symptoms manifest.

Complications of fever

Febrile convulsions in children are seizures triggered by fever. Consult a doctor if concerned.

Resources and support

If you have urgent concerns, contact the healthdirect helpline at 1800 022 222.

Source:

Information obtained from various reputable sources.

Last reviewed: March 2024

Search our site for

Types of thermometers
Information on fever-reducing medications

Need more information?

For more information on this topic, consult trusted information partners.

Fever and high temperature: kids and teens | Raising Children Network

If your child has a temperature exceeding 38°C, it could indicate a fever. Follow appropriate steps for managing fevers in children.

Further details available on the raisingchildren.net.au website

Fever in Children – Rahma Health

A fever is characterized by a temperature of over 38 degrees Celsius.

Find more information on fevers at the Rahma Health website

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Category: About child care