The Lung Yin is responsible for moistening the Lungs, skin and upper body internal cavities. The Stomach Yin is closely related to the Lung Yin, but it is responsible for nourishing the stomach and ensuring proper digestion takes place. When the Yin of the Stomach and Lungs is deficient, problems of internal dryness result, thereby creating other problems of internal heat and stagnation. The Lung Yin and Stomach Yin can become deficient from poor diet (with rich foods), smoking, and excess grief (whether present or historically).