35.8℃ is not a low fever, it is hypothermia, which is caused by more reasons, and should be promptly seen by the internal medicine department of the hospital to clarify the cause and give appropriate treatment. The main clinical sites for temperature detection are anorectal, oral and axillary, and the common detection site is in the axilla. Its normal value is 36.3℃-37.2℃ for oral sublingual temperature, 36.5℃-37.7℃ for rectal temperature, and 36.0℃-37.0℃ for axillary temperature. Therefore, a body temperature of 35.8°C is considered hypothermic and suggests the possibility of a serious infection or hypothyroidism. If necessary, wipe the axilla clean and retake the temperature for no less than 5 minutes. When the axillary body temperature is 37℃-37.9℃, it belongs to the case of hypothermia, which generally suggests the presence of infection, commonly including cold, upper respiratory tract infection, urinary tract infection, lung infection, intestinal infection, etc. Relevant examinations should be improved promptly to clarify the foci of infection, active anti-inflammatory treatment, and application of rehydration and antipyretic drugs if necessary. In addition, it is recommended to pay attention to diet and nutrition, prevent cold and keep warm, do not stay up late, pay attention to rest, avoid smoking, alcohol and spicy and stimulating diet.