The fact that the fever goes down after a bowel movement and comes back at night is usually related to the heat dissipation of the bowel movement, the weakening of the thermoregulatory center at night, and the fact that the cause of the illness has not been eliminated. The reason why the fever goes down after having a bowel movement is that the digestive tract is also a way for the body to dissipate heat. The digestive tract itself is covered by mucous membranes, and there are abundant blood vessels in the center, the area is relatively large, these blood vessels dilation will also produce the effect of heat excretion. The process of defecation is also a way to dissipate heat, so there may be a situation where the fever goes down after having a bowel movement. The reason why you have a fever at night is because your body’s thermoregulatory center is not as strong as it is during the day, and your ability to regulate it is weakened. If the fever goes down at night, it may be because the cause of the fever itself has not been eliminated, and the bowel movement only temporarily relieves the body temperature, but does not solve the problem that caused the fever at all. There may be other reasons for the fever to return at night, so it is recommended that you go to the hospital in time to have the cause of the fever clarified, and then give targeted treatment or therapy.