What causes cold back?

There were two main reasons for the cold in the back. One was the lack of yang qi, and the other was that the circulation of yang qi was hindered. From the perspective of yin and yang, the back belonged to the yang surface. Moreover, the bladder meridian, which was the yang meridian with the most vigorous yang qi among the twelve meridians, and the governor meridian, known as the "sea of yang meridians," were distributed on the back of the body. In other words, if the yang qi in these two meridians was not circulating smoothly, or if the yang qi was insufficient, it would show a feeling of cold in the back. Feel the wind evil and cold evil in nature, belonging to yin evil, which is the most likely to harm yang qi; if you eat seafood and other bitter and cold foods for a long time, it is also easy to damage the yang qi of the body.