The main causes of fever in the human body are infections, malignant tumors and other non-infectious diseases. It is recommended to consult a doctor in time to identify the cause of the disease and carry out symptomatic treatment. 1. Infection: mainly bacteria, viruses, mycoplasma and other pathogens invade the human body, producing thermogenic factors, under the stimulation of the thermogenic factors, the body’s immunity decreases, the body temperature will shift, thus leading to the emergence of human fever. 2. Non-infectious factors: mainly including malignant tumors, leukemia and other serious diseases; hyperthyroidism and other endocrine disorders or metabolic diseases; rheumatic fever and other allergic reactions; chronic heart failure; autonomic dysfunction and other diseases. All of these diseases may be accompanied by the appearance of human fever. Fever is recommended to consult a doctor in time to clarify the cause of the disease and timely treatment.