Bitterness in the mouth after a fever is generally not directly related to fever. It is considered to be related to the condition, because fever is usually caused by digestive or respiratory diseases, indicating that there is fire in the body, poor digestion, excess heat and moisture, or infection in the respiratory tract, which causes the body temperature to increase. After taking bitter-cold medicine, the body temperature can return to normal, but due to poor digestion, bitterness in the mouth may occur. If the fever is caused by digestive system diseases, it may be due to the disease has not been completely healed, although the body temperature has returned to normal, but the digestive system symptoms have not been completely healed, and there are symptoms of regurgitation, nausea, diarrhea, or bitterness in the mouth, which still need some time to recover. Pay attention to a light diet and reduce the intake of high-calorie food, which is also known as stomach qi not completely recovered in Chinese medicine. Simple respiratory infections can be treated symptomatically, and after a period of improvement, the problem of bitterness in the mouth will be relieved.