Conditions Directory

Causes of Fever
Fever is not an illness itself but a symptom of an underlying condition. It occurs when an area in the brain called the hypothalamus, which acts as the body's thermostat, shifts the set point of normal body temperature upward. This shift is usually a response to substances called pyrogens, which can come from outside the body (such as bacteria or viruses) or from the body's own immune system. The most common cause of fever is infection, but it can be triggered by many different factors. Common causes include:

• Viral infections, such as the flu, the common cold, or COVID-19.
• Bacterial infections, such as strep throat, ear infections, or urinary tract infections.
• Heat exhaustion or extreme sunburn.
• Inflammatory conditions, including rheumatoid arthritis and lupus.
• Side effects of certain medications, such as antibiotics or drugs used to treat high blood pressure.
• Immunizations, which often cause a mild, temporary fever as the immune system builds protection.

Risk Factors
Anyone can develop a fever, but certain factors increase the likelihood of exposure to the infections that cause them. Environmental and lifestyle factors play a significant role. Key risk factors include:

• Close contact with someone who is sick.
• Having a weakened immune system due to age or medical conditions.
• Spending time in crowded environments like schools or daycare centers.
• Eating or drinking contaminated foods or water.

Prevention
Preventing fever primarily involves avoiding the infectious diseases that cause it. While not all fevers can be prevented, especially those caused by non-infectious conditions, basic hygiene and health measures significantly reduce the risk. Effective prevention strategies include:

• Washing hands frequently with soap and water, especially before eating and after using the restroom.
• Staying up to date with recommended vaccinations for influenza, pneumonia, and other preventable diseases.
• Avoiding sharing cups, water bottles, or utensils with others.
• Maintaining a healthy lifestyle with adequate sleep and nutrition to support immune function.

Signs and Symptoms
The primary sign of a fever is a body temperature that is higher than normal, generally considered to be 100.4 degrees Fahrenheit (38 degrees Celsius) or higher. Beyond the number on the thermometer, fever is often accompanied by physical sensations that indicate the body is trying to regulate its temperature. Symptoms may vary depending on the cause of the fever and the age of the person affected. Common associated symptoms include:

• Sweating and warm skin.
• Chills and shivering.
• Headache and muscle aches.
• Loss of appetite.
• Irritability or general weakness.
• Dehydration.

Diagnosing Fever
Clinicians and caregivers identify fever by measuring body temperature using a thermometer. Different types of thermometers are available, including oral, rectal, ear (tympanic), and forehead (temporal artery) scanners. Rectal thermometers are generally considered the most accurate for infants and young children. If a fever is persistent or accompanied by severe symptoms, a doctor may perform further evaluations to identify the underlying cause. Diagnostic tools may include:

• Physical examination to look for signs of infection like a sore throat or ear infection.
• Blood tests, such as a complete blood count, to detect elevated white blood cells.
• Urinalysis to check for urinary tract infections.
• Chest X-rays if respiratory issues like pneumonia are suspected.
• Swab tests for specific viruses like influenza, strep, or COVID-19.

Treatment and Management Strategies
Low-grade fevers often do not require medical treatment and may help the body fight off infection. However, when a fever causes discomfort or reaches high levels, management focuses on relieving symptoms and preventing dehydration. The underlying cause of the fever, such as a bacterial infection, must be treated separately if necessary (for example, with antibiotics). Common management strategies include:

• Getting plenty of rest to allow the body to recover.
• Drinking fluids like water, broth, or electrolyte solutions to prevent dehydration.
• Keeping the room temperature comfortable and wearing lightweight clothing.
• Using over-the-counter medications like acetaminophen or ibuprofen to lower temperature and reduce body aches.
• Using a lukewarm sponge bath to help cool the body down (avoiding cold water, which can cause shivering).

When to Seek Medical Care
While most fevers are harmless, certain situations require professional medical attention. The urgency depends on the person's age and accompanying symptoms. It is important to monitor for red-flag signs that indicate a more serious condition. You should seek medical care if:

• An infant younger than 3 months has a rectal temperature of 100.4 degrees F (38 degrees C) or higher.
• A child between 3 and 6 months has a temperature up to 102 degrees F (38.9 degrees C) and seems unusually irritable or lethargic.
• A fever lasts longer than three days despite home treatment.
• The fever is accompanied by a severe headache, stiff neck, skin rash, or sensitivity to bright light.
• There is difficulty breathing, persistent vomiting, or abdominal pain.
• Confusion, convulsions, or seizures occur.

Severity and Disease Course
Fever severity is generally categorized by the height of the temperature and the accompanying symptoms. Most fevers are mild and self-limiting, resolving within a few days as the immune system clears the infection. Acute fevers typically last less than a week. In some cases, a fever may be "fever of unknown origin," lasting for weeks without an immediately obvious cause, which requires extensive medical investigation. The course of the fever tracks with the underlying illness; for example, a viral fever usually peaks and then gradually subsides.

Complications
While the fever itself rarely causes permanent harm, high body temperatures can lead to complications, particularly in vulnerable populations. The most common complication is dehydration due to increased metabolic rate and fluid loss through sweating. In children between the ages of 6 months and 5 years, high fevers can sometimes trigger febrile seizures. These seizures involve shaking and loss of consciousness but usually have no lasting effects. Severe complications are typically related to the underlying disease (such as meningitis or sepsis) rather than the fever itself. Serious risks include:

• Severe dehydration requiring intravenous fluids.
• Febrile seizures in young children.
• Heat stroke if the body temperature rises to dangerous levels due to environmental heat rather than infection.
• Worsening of chronic conditions like heart or lung disease due to the increased metabolic demand.

Prognosis
The prognosis for someone with a fever is usually excellent. Once the viral or bacterial infection clears, body temperature returns to normal with no long-term consequences. In cases where fever is a symptom of a chronic or autoimmune condition, the fever may recur during flare-ups. Early diagnosis and treatment of the underlying cause are the most important factors in determining the outcome.

Impact on Daily Activities
A fever often necessitates a temporary pause in daily routines. The physical symptoms, such as fatigue, aches, and chills, make it difficult to concentrate on work or school. Rest is a critical component of recovery, meaning individuals should stay home to recuperate and prevent spreading any potential infection to others. This can lead to short-term social isolation and disrupted schedules. Parents often need to take time off work to care for feverish children, adding to logistical stress. Hydration and rest become the primary focus of the day until the temperature normalizes.

Questions to Ask Your Healthcare Provider
To better understand the situation and ensure safety, it is helpful to have a list of questions ready for a doctor's appointment. These questions can help clarify the cause of the fever and the best path forward. Consider asking:

• What is the most likely cause of this fever?
• Are there any specific tests needed to rule out serious infections?
• How long should I expect the fever to last?
• At what temperature should I be concerned or go to the emergency room?
• Which over-the-counter medications are safe to use, and at what dosage?
• Are there signs of dehydration I should watch for?
• When can I (or my child) safely return to work, school, or daycare?

Q: What is considered a high fever for an adult?
A: For adults, a fever is generally considered high if it reaches 103 degrees Fahrenheit (39.4 degrees Celsius) or above. While lower fevers can cause discomfort, temperatures at this level often warrant a call to a healthcare provider to check for serious underlying causes.

Q: Is it true that you should "starve a fever"?
A: No, the old saying "starve a fever, feed a cold" is a myth. When you have a fever, your body burns more calories and loses fluids more rapidly to fight the infection. It is important to stay hydrated and eat nutrient-rich foods if you have an appetite to support your immune system.

Q: Can a fever cause brain damage?
A: Fevers caused by infections generally do not go high enough to cause brain damage. Brain damage is a risk only when body temperature exceeds 107.6 degrees Fahrenheit (42 degrees Celsius), which rarely happens with common infections but can occur with extreme environmental heat stroke.

Q: Should I wake a sleeping child to give them fever medicine?
A: Generally, it is best to let a sleeping child rest. Sleep is crucial for recovery, and if the child is sleeping comfortably, the fever is likely not causing significant distress. You can administer medication when they wake up if they are uncomfortable or if advised by a doctor.

Q: Why do I feel cold when I have a fever?
A: You feel cold and may shiver because your body is trying to raise its core temperature to a higher set point determined by the hypothalamus. Shivering is a muscle activity that generates heat to help reach this new temperature target.