Chills

Chills is a feeling of coldness occurring usually during a high fever but sometimes alone in specific people. It occurs during fever as a result of 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 chilled until the new set point is reached. The patient will also shiver because their body produces heat during muscle contraction in a physiological attempt to increase body temperature to the new set point. Chills not accompanying a high fever are normally mild. A scare, especially one of fear, may cause a chill of medium power and short duration; this is commonly interpreted as or confused with trembling. Severe chills with violent shivering are called rigors.