Sub-health” in traditional medicine We usually say that we have a disease, but in ancient times “disease” and “illness” have different meanings. “Sickness” refers to a small disease that is not easily detectable, but if effective measures are not taken, it will develop to a visible degree and is called “disease”. This state of illness is called “subhealth” or “third state” in modern science, and “undisease” in Chinese medicine. The so-called subhealth state, in common parlance, refers to a state of low quality and psychological imbalance without clinical symptoms and signs, or with the feeling of illness without clinical evidence, but with the information of potential pathogenic tendency. Generally speaking, subhealth state consists of four major elements: fatigue and weakness excluding disease, intermediate or pre-disease state between health and disease, imperfect state in physical, psychological, social adaptability and morality, and age-inappropriate decline of tissue structure and physiological function. “According to the viewpoint of traditional Chinese medicine, the body is already in a state of imbalance between yin and yang, qi and blood, and the internal organs and health. Our ancestors have long been aware that in addition to actively seeking ways to eliminate diseases, they have also accumulated many measures to prevent them. The Yellow Emperor’s Classic of Internal Medicine says: “The sage does not treat the sick to treat the sick, and the sick have become and then medicine, chaos has become and then cure, like thirst and wear a well, the bucket and cast a soldier, is not also late?” This clearly shows that our ancestors have recognized the importance of “preparing for the rainy days and taking precautions against diseases”.