Fever, also known as pyrexia and febrile response,[6] is defined as having a temperature above the normal range due to an increase in the body's temperature set point.[4][5] There is not a single agreed-upon upper limit for normal temperature with sources using values between 37.5 and 38.3 °C (99.5 and 100.9 °F).[6][7] The increase in set point triggers increased muscle contractions and causes a feeling of cold.[5] This results in greater heat production and efforts to conserve heat.[2] When the set point temperature returns to normal, a person feels hot, becomes flushed, and may begin to sweat.[2] Rarely a fever may trigger a febrile seizure.[3] This is more common in young children.[3] Fevers do not typically go higher than 41 to 42 °C (105.8 to 107.6 °F).[5]