Humans and other mammals have a relatively stable body temperature, and a variety of physiological and pathological factors can cause an increase in body temperature, including physiological elevation, hyperthermia, and fever. Fever refers to the production and release of endogenous pyrogen by thermogenic cells under the action of fever activators, which acts on the hypothalamic thermoregulatory center, mediated by the central thermogenic mediators, causing an upward shift of the thermoregulatory point, which in turn causes an increase in heat production and a decrease in heat loss, ultimately leading to an increase in body temperature. Fever is not an independent disease, but a pathophysiological process and clinical manifestation common to many diseases, and changes in body temperature are often closely related to the disease process in the body. Fever usually goes through 3 phases: rising body temperature, persistent high temperature and falling body temperature. 1.Rising body temperature period: the body’s heat production increases, heat loss decreases, heat production is greater than heat loss, and this process makes the body temperature rise continuously. Children with a sudden rise in body temperature often have chills and may have convulsions. 2.High fever period: When the body temperature rises to the new level of the adjustment point by increasing heat production and reducing heat dissipation, it starts to regulate the heat production process and heat dissipation process at a high level, so that the high temperature can be sustained, called the high temperature duration. The duration may vary depending on the cause of the disease. At this time, as the skin temperature also rises, no more cold stimulation information occurs, and therefore no more shivering is produced, and this period mainly relies on increasing the metabolic rate to maintain the increased heat production process. Due to the relief of skin vasoconstriction and the increase of skin blood flow, heat dissipation also increases during this period. That is, the heat production process and the heat dissipation process reach a balance at a high level. 3. Decrease in body temperature: When the cause of the fever is effectively controlled by the application of drugs, the endogenous thermogenic substances are removed and the body temperature regulating point is restored to normal level, the body increases the heat dissipation process to lower the increased body temperature to the normal regulating point level and the body temperature returns to normal. During this period, the heat dissipation process can be significantly enhanced due to reduced sympathetic nervous activity, skin vasodilation and enhanced sweat gland secretion. Different diseases can have different fever patterns, according to which it helps in the differential diagnosis of diseases. A certain degree of fever is good for the body to resist infection and remove pathogenic factors that are harmful to the body, but when the body temperature rises too much and lasts for a long time, it causes a series of functional and metabolic changes in the body. Treatment should be tailored to the cause and condition of the fever, and if necessary, appropriate antipyretic measures can be taken to address the basic aspects of fever pathogenesis while treating the primary cause.