If there is a recent cold in the undershirt, in this case it may be caused by external wind and cold, and can be treated with drugs that disperse cold and relieve the symptoms. If the back is cold for a long period of time, it may be due to the following conditions: First, insufficient yang qi, yin cold inside, some patients may also have cold extremities and a sinking pulse, so it is recommended to use Si Wei Tang. Second, cold phlegm can also cause coldness in the back. It is recommended to perform further rheumatism-related examinations to exclude rheumatic diseases, such as blood count, blood sedimentation, rheumatism triad, anti-nuclear antibody, etc. Fourth, the coldness of the back may also be caused by external cold, cold dampness or Yangming meridian heat. Fifth, patients with gastrointestinal dysfunction or weakness can also have a cold back. This condition is due to the low ability of the body to disperse heat, poor resistance, and low resistance to cold. Sixth, women who have been in a state of nutritional deficiency for a long time, suffering from anemia, hypotension and thyroid dysfunction, can also cause poor local and systemic blood circulation, which can cause a cold discomfort in the back. Dietary imbalance, especially in the summer, the greed for raw and cold food, the consumption of Yang Qi, in the autumn and winter will easily cause the cold back. Good static and little movement, slow blood circulation, insufficient heat production capacity, will also aggravate the undershirt cold feeling in winter.