PCN Art Brut Series No. 52, Artwork Description.

Fever remains among the most common reasons for consultation in pediatric emergency departments [] and illustrates how caregiver behaviour is shaped by cultural beliefs and cognitive biases, most notably the persistent phenomenon of “fever phobia” []. Despite robust evidence that most childhood fevers are self-limited and benign, anxiety about elevated body temperature continues to drive premature or excessive interventions. Practices such as alternating antipyretics or administering medication at the first sign of fever or with the sole aim of lowering the temperature remain common, although supportive evidence is limited []. This discrepancy underscores the ongoing need for accessible, evidence-based guidance that situates fever within physiological norms and supports appropriate decision-making []. Chronobiology provides an important framework for such contextualisation. In healthy individuals, core body temperature follows a well-described circadian rhythm, typically fluctuating by around 1 °C over 24 h [, ]. The nadir usually occurs in the early morning (approximately 04:00–06:00), followed by a rise toward an afternoon or early-evening peak [, ]. This rhythm is closely linked to hormonal cycles (e.g., cortisol and melatonin) and central thermoregulatory pathways []. In U.S. national triage data, fever detection was substantially lower in the morning than later in the day, and high-grade fever (> 39 °C) was comparatively uncommon before 09:00 []. Although atypical courses exist (e.g., persistent fever or irregular trajectories), diurnal variation remains a common feature in uncomplicated viral and bacterial illness []. Despite these established principles, diurnal patterns of pediatric fever remain insufficiently characterised outside institutional settings. High-frequency, time-stamped temperature data from the home environment have traditionally been scarce; app-based registries now enable ecological capture of fever trajectories at scale [, ]. Applications such as FeverApp allow caregivers to document temperature, symptoms, and medication use in real time, generating ecologically valid datasets for chronobiological and clinical analyses []. Beyond functioning as a digital fever diary, FeverApp was designed as a participatory research platform, enabling caregivers to contribute structured real-world data while receiving guideline-based support for fever management []. This approach aligns with broader developments in public health and digital citizen science, including efforts to strengthen public trust and engagement in real-world evidence generation [].