Rigor (medicine)

Chills
Classification and external resources
ICD-10	R50.0
ICD-9-CM	780.64
MedlinePlus	003091
Patient UK	Chills
MeSH	D023341
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Chills is a feeling of coldness occurring during a high fever, but sometimes is also a common symptom which occurs alone in specific people. It occurs during fever due to the release of cytokines and prostaglandins as part of the inflammatory response, which increases the set point for body temperature in the hypothalamus. The increased set point causes the body temperature to rise (pyrexia), but also makes the patient feel cold or chills until the new set point is reached. Shivering also occurs along with chills because the patient's body produces heat during muscle contraction in a physiological attempt to increase body temperature to the new set point. When it does not accompany a high fever, it is normally a light chill. Sometimes a chill of medium power and short duration may occur during a scare, especially in scares of fear, commonly interpreted like or confused by trembling.

Severe chills with violent shivering are called rigors.

Chills are commonly caused by inflammatory diseases, such as the flu.Malaria is one of the common reasons for chills and rigors. Sometimes they happen in specific people almost all the time, in a slight power, or it less commonly happens in a generally healthy person.

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