View source for Chills

{{SignSymptom infobox |
  Name        = Rigor  |
  ICD10       = {{ICD10|R|50|0|r|50}} |
  ICD9        = {{ICD9|780.64}} |
  MeshID      = D023341 |
}}
{{dablink|For the New Zealand rock band, see [[The Chills]].}}

'''Rigor'''  is a [[tremor|shaking]] occurring during a high [[fever]]. It occurs because [[cytokine|cytokines]] and [[prostaglandin]]s are released as part of an [[immune response]] and increase the set point for body temperature in the [[hypothalamus]].

It is sometimes considered a synonym for "chills".<ref>{{DorlandsDict|seven/000093311|rigor}}</ref>

==Physiology==
The increased set point causes the body temperature to rise ([[pyrexia]]), but also makes the patient feel cold until the new set point is reached. Rigor occurs because the patient is effectively shivering in a physiological attempt to increase body temperature to the new set point.

==Causes==
Rigors are commonly caused by:

* [[Influenza]]
* [[Tonsillitis]]
* Infectious [[Pneumonia]] 
* [[Biliary]] sepsis (part of [[Charcot's triad 2]])
* [[Pyelonephritis]]
* Visceral [[abscess]] (including lung, liver and paracolic) 
* [[Malaria]]
* A side effect of treatment with [[amphotericin B]]

==See also==
* [[Rigor mortis]]
* [[Shivering]]

==References==
{{reflist}}

{{General symptoms and signs}}
[[Category:Symptoms]]

[[ca:Calfred]]
[[de:Schüttelfrost]]
[[es:Escalofrío]]
[[ko:오한]]
[[ja:悪寒]]
[[ru:Озноб]]
[[sv:Frossa]]
[[uk:Озноб]]
[[Category:2Fix]]