"Avoiding pathogenic influences and damaging winds in due season" is a concise yet inclusive scripture in Huangdi Neijing that not only focuses on avoiding pathogenic qi in the four seasons but is also explained from the two perspectives of "three deficiencies" and "eight cardinal directions." First, in terms of "three deficiencies," in the year of overrestraint, we should avoid the conquest of abnormal changes of climate from the first to third qi, and avoid the retaliation of abnormal changes of climate from the fourth qi to last; second, on the first day of each lunar month and one to two days before and after, the human body is in a weak state under the influence of the moon; therefore, deficient nature pathogens should be avoided. Third, when the solar terms are exchanged, climate changes should be observed to anticipate them. In terms of "eight cardinal directions," we should prevent abnormal wind and rain, which come early or late around the eight solar terms (Beginning of Spring, the Spring Equinox, the Beginning of Summer, the Summer Solstice, the Beginning of Autumn, the Autumn Equinox, the Beginning of Winter, and the Winter Solstice). In contrast, especially on the day of the eight solar terms, the wind coming from the opposite direction of the corresponding solar terms should be paid attention to, as this wind is violent and easily opens the pores to cause disease. Therefore, it is necessary to stay indoors on such days. Additionally, the wind, coming from the rest of the six directions in addition to the direction and the opposite direction of the corresponding solar terms, on the first day of the first month of the lunar calendar, is regarded as the basis for predicting the prevalence of diseases of the coming year, which also needs special attention. Therefore, "avoiding pathogenic influences and damaging winds in due season" must be deeply interpreted to fully use the Huangdi Neijing to prevent and treat diseases.

In traditional Chinese medicine theory, the skin is one of the five body constituents, and its connotations are described through multiple interpretations and expressions in Huangdi Neijing. The concept of the skin encompasses fine hair, striae and interstices (couli), and superficial collaterals, reflecting diverse medical perspectives and understandings of the skin. The functions of the skin are also reflected through its associated structures. With the development of the theories of meridians and visceral systems, the skin, as a bodily tissue, became integrated with these systems, forming various correlation patterns. The qi and blood of the entire body nourish the skin and fine hair, and their condition serves as an external indicator of the abundance or deficiency of qi and blood. As the lung governs qi and regulates respiration, providing the dynamic force for the circulation of qi and blood, the concept of "lung governs the skin and hair" emerged. The notion that "taiyang governs the exterior" originated from the integration of meridian theory with the skin, muscles, and bones. It represents an early diagnostic approach that combined bodily tissue differentiation with meridian differentiation for febrile diseases caused by external pathogens. "Heart governs the exterior" is closely associated with early bloodletting therapies. The superficial collaterals on the body surface are considered extensions of the function of the heart governing blood circulation. Bloodletting method was believed to promote blood circulation, purge heart fire, and regulate mental activity. This paper investigates the concept and connotation of skin and the construction of its relevant theoretical framework, aiming to address the current gaps in the understanding of skin theory and contribute to the enrichment and refinement of the theory of bodily constituents in Huangdi Neijing.

Traditional Chinese medicine (TCM) has a comprehensive and thorough understanding of biological rhythm. Biological rhythm is an inherent connotation of “harmony between human and nature”, one of the thoughts in TCM. TCM discusses emphatically circadian rhythm, syzygial rhythm and seasonal rhythm, and particularly circadian and seasonal rhythms. Theories of Yin Yang and Five Elements are the principles and methods, with which TCM understands biological rhythms. Based on theories in TCM, biological rhythm in essence is a continuous variation of the human body state synchronized with natural rhythms, and theories of Yin Yang and Five Elements are both language tools to describe this continuous variation and theoretical tools for its investigation and application. The understandings of biological rhythm in TCM can be applied to etiology, health care, disease control and treatment. Many understandings in TCM have been confirmed by modern research and clinical reports, but there are still some pending issues. TCM is distinguished for its holistic viewpoint on biological rhythms.