A fever, defined as a body temperature at or above 100.4°F (38°C), is a symptom indicating that the body’s immune system is actively working to combat an infection or illness. This elevated temperature enhances the immune response, which can make it more challenging for certain pathogens to thrive and can stimulate the production of immune cells and proteins.
Typical Fever Duration
The duration of a fever can vary significantly based on the underlying cause. Many fevers, particularly those resulting from common viral infections like the cold or flu, typically last between 2 to 3 days, sometimes extending up to 5 days. In some instances, a viral fever might resolve in as little as one day, while more severe cases could persist for up to 7 to 10 days, or even beyond two weeks in certain viral infections like dengue or COVID-19. The length of the fever is influenced by factors such as the specific type of virus, the individual’s overall health, and their immune system’s response. Even after the fever subsides, other symptoms like fatigue or muscle aches might linger for several additional days or weeks, depending on the virus.
Signs to Seek Medical Care
While many fevers resolve without complication, certain signs and symptoms indicate a need for prompt medical evaluation, with concerns varying across age groups.
Infants younger than 3 months old with any fever (a rectal temperature of 100.4°F (38°C) or higher) should receive immediate medical attention. Even a low-grade fever in this age group can signal a serious infection. If a pediatrician is unavailable, proceed to an emergency department.
For older infants and children, seek medical consultation if a fever reaches 104°F (40°C) or higher, persists for more than 3 to 5 days, or does not decrease with medication. Other warning signs include extreme irritability or lethargy, difficulty breathing, a stiff neck, severe headache, persistent vomiting or diarrhea, a rash, or signs of dehydration like decreased urination or sunken eyes. Seizures, even if fever-related, also require medical evaluation.
Adults should seek medical attention if a fever reaches 103°F (39.4°C) or higher, or lasts over 3 to 5 days. Accompanying severe symptoms, such as a stiff neck, intense headache, shortness of breath, chest pain, abdominal pain, confusion, or seizures, also warrant consulting a healthcare provider. A rash or unusual light sensitivity with fever is also concerning. Medical advice is recommended if a fever worsens quickly or has no clear cause.
Immunocompromised individuals (e.g., due to cancer, HIV, or organ transplantation) should contact their doctor for any fever. Their weakened immune systems make them susceptible to severe infections, and symptoms can be subtle or atypical, requiring prompt evaluation and treatment.
Fever Management at Home
When no concerning symptoms are present, managing a fever at home focuses on comfort and supporting the body’s natural healing. Maintain adequate hydration, as fever can lead to fluid loss through sweating. Drink plenty of fluids like water, clear broths, or electrolyte solutions to prevent dehydration.
Rest is beneficial, allowing the body to conserve energy and focus on recovery. Comfort measures include wearing light clothing and using cool compresses to regulate body temperature. Lukewarm baths can provide relief, but avoid cold baths or ice packs as they can cause shivering and potentially increase body temperature.
Over-the-counter medications like acetaminophen and ibuprofen can reduce fever and alleviate discomfort. Follow dosage instructions on the label, which are based on age and weight, and consult a doctor, especially for children. Aspirin should not be given to children or teenagers due to the risk of Reye’s Syndrome, a rare but serious condition. Monitor temperature and observe for any symptom changes during home management.