Fever in the feet while sleeping is related to high environmental temperature, metabolic disorders, and rheumatic immune diseases. 1. Excessive environmental temperature: If the living environment has a high temperature, or the room is closed and impermeable to air, it may lead to body heat and feet heat when sleeping. 2. Metabolic disorders: For example, when the metabolic rate is accelerated, it may promote blood circulation and lead to an increase in cellular heat production, thus causing hot feet and hot body. 3. Rheumatic immune diseases: such as rheumatoid arthritis, gout, arthritis, etc., these diseases may lead to inflammatory reactions in the feet, triggering fever and other phenomena, and in severe cases, it can also cause joint deformation, joint pain. In addition to the above factors, hot feet during sleep may also be related to other factors, such as infection with tuberculosis bacilli, hyperthyroidism, and so on. In order to clarify the cause, it is recommended to consult a doctor in time and analyze the cause of the disease through relevant examinations, and then target treatment.