What is Fever?
Although often used interchangeably, the terms fever and hyperthermia refer to different processes, and the distinction is key. In fever the thermoregulatory set-point is elevated, and the body actively raises its temperature with chills and rigors to reach the new set-point. In hyperthermia the body’s temperature exceeds the set-point, due to increased heat production (eg hypermetabolic state) or decreased dissipation (eg high humidity or ambient temperature).1
Fever is generally defined as temperature ≥38°C (100.4°F) and results from a complex mechanism. The body produces pyrogens (specific cytokines) that act on the thermoregulatory center in the hypothalamus to increase the set-point. This is thought to occur by increased prostaglandin synthesis, and antipyretic drugs lower the set-point likely by inhibiting prostaglandin synthesis.2 There are also numerous endogenous antipyretics (cryogens).
Increased temperatures enhance immune function in many ways, including improved neutrophil migration and secretion of antibacterial substances, increased interferon, and increased T cell proliferation.1
A 1980 study titled “Fever phobia: misconceptions of parents about fever” surveyed parents, and found 94% thought fever may have harmful effects, 18% thought brain damage or serious harm could result from fever <38.9°C (102°F), and 16% thought fever could rise up to 48.9°C (120°F) if untreated.3 A 2001 study re-examined similar questions, and found 76% believed serious harm could occur at ≤40°C (104°F).3
This phobia also exists among healthcare workers. A 1992 survey by the American Academy of Pediatrics in Massachusetts showed 65% of pediatricians thought fever alone is potentially dangerous, 72% “always or often” prescribed antipyretics for fever, and 89% recommended antipyretics for fever of 101-102°F.4 A 2000 study of pediatric emergency department nurses, with a median experience of 8 years, found 11% were unsure what temperature constituted fever, 29% thought permanent brain injury or death could occur from high fever, and 18% believed it is dangerous for children to be discharged from the emergency department if still febrile.5
Is Fever Harmful?
Some providers have concerns that the increased temperature or metabolic demand from fever will harm patients. Humans generally tolerate temperatures below 41°C (105.8F) without harm. In contrast to hyperthermia, it is extremely rare for fever as a host defense against infection to reach dangerous temperatures in neurologically normal patients, since the body is actively adjusting both the set-point and actual temperature.3 A 2011 American Academy of Pediatrics policy paper states “There is no evidence that fever itself worsens the course of an illness or that it causes long-term neurologic complications.” 6 Continue reading