45. The Principles of Oriental Medicine ： Yin and Yang 4

4. The Wane and Wax of Yin and Yang (陰陽消長) — Yin Deficiency Syndrome

The concept of “wane and wax of yin and yang” (陰陽消長) means that yin and yang in nature are not static but constantly move and change. The alternation of cold and heat through the seasons, the longest day during the summer solstice, and the longest night during the winter solstice are all results of the dynamic changes of yin and yang. Similarly, the human body corresponds to the rhythms of nature, undergoing continuous changes in yin and yang.

However, when the balance of yin and yang exceeds certain limits—where one becomes too excessive or too deficient—the harmony collapses, leading to pathological conditions such as yin deficiency (陰虛症), yang deficiency (陽虛症), or combined yin-yang deficiency (陰陽兩虛症).

Yin deficiency syndrome (陰虛症), or deficiency of yin or essence (精), refers to symptoms caused by a lack of body fluids such as hormones or endocrine secretions. Common symptoms include low-grade fever, depression, memory decline, and dry skin. If yin deficiency persists over time, it may lead to yin deficiency with hyperactive fire (陰虛火旺)—a condition where internal heat rises due to the yin being depleted. In such cases, the head feels hot from floating false heat, while the lower abdomen feels cold due to insufficient yang energy, resulting in a pattern known as upper heat and lower cold (上熱下寒).

Typical symptoms include facial flushing, tinnitus (ringing in the ears), alternating chills and fever (寒熱往來), palpitations, sleep disturbances, and hair loss. This syndrome often appears during menopause, around the age of 50, when yin energy declines significantly.

Basic self-care measures include consuming black-colored foods such as black beans and black sesame to replenish yin energy, going to bed before 11 PM to prevent the depletion of body fluids, and doing 20 minutes of foot bathing before sleep each night to warm the feet and cool the head.

Dr. Jin-man Kim, director of Peace Oriental Clinic