What Is Fever in Children

Fever refers to an elevation of body temperature above the upper limit of the normal range and is a common clinical symptom. In healthy individuals, axillary (underarm) temperature normally ranges from 36°C to 37°C. Rectal temperature is approximately 0.3°C higher than oral temperature, while oral temperature is about 0.4°C higher than axillary temperature. An axillary temperature exceeding 37.4°C is generally considered indicative of fever. What is fever in children?

What Is Fever in Children?

Fever in children refers to a body temperature exceeding the upper limit of the normal range and is the most common symptom encountered in pediatric clinical practice. Axillary temperature measurement is routinely used to assess fever in children. The normal axillary temperature range for children is 36–37°C. Fever severity is typically classified as follows: low-grade fever (37.5–38.0°C), moderate fever (38.1–39.0°C), high fever (39.1–40.4°C), and hyperpyrexia (≥40.5°C).

Clinical Stages and Key Manifestations of Fever in Children
1. Prodromal Phase: Many febrile illnesses may lack this phase entirely. When present, its duration varies depending on the specific underlying disease. Common manifestations include generalized malaise, fatigue, lumbosacral and limb pain, headache, decreased appetite, emotional instability, and low-grade fever. In certain exanthematous diseases, characteristic prodromal rashes may appear before the generalized rash—for example, Koplik spots on the buccal mucosa during the prodromal phase of measles.

Fever is clinically categorized by duration: fever lasting less than seven days is termed acute fever, whereas fever persisting for two weeks or longer is classified as prolonged fever. During fever, children commonly experience marked fatigue and reduced appetite, often accompanied by other symptoms. Fever in children has diverse etiologies—including both infectious and non-infectious causes. Therefore, when a child develops fever, prompt identification of the underlying cause is essential to guide appropriate, etiology-directed treatment. We hope this information is helpful to you.