Characteristically, a hot flash (also called hot flush) is a sudden feeling of warmth and often a breakout of sweating usually confined to the upper half of the body (chest and up), neck, face and head. There is an intense feeling of heat and the face head and neck can turn red. When they occur at night, they are called "night sweats". It can be difficult to distinguish them from a low grade fever such as that seen with the flu, a cold, a urinary tract infection or a more serious cause of fever such as tuberculosis or cancer. Fevers usually cause the sweating to last longer than the typical few seconds or few minutes that hot flashes last. Non fever caused hot flashes can occur rarely or every few minutes.