Located on the outermost layer of our body, the skin goes beyond a simple covering organ to act as an essential skin barrier that protects against external harmful substances and prevents moisture loss. The most critical components of this barrier are keratinocytes and the intercellular lipids filling the spaces between them, namely ceramides, cholesterol, and fatty acids. These lipid components fit tightly together like cement between bricks, preventing internal moisture from evaporating.
Dry skin indicates a weakened skin barrier function. When the barrier is damaged, the skin loses moisture more easily and becomes vulnerable to external irritants such as allergens and bacteria. Consequently, the skin dries out further and develops pruritus even from minor stimuli. When an itch strikes, we scratch unconsciously, which further damages the skin barrier, triggers an inflammatory response, and ultimately causes greater dryness and itching. This is known as the itch-scratch cycle.
Furthermore, modern medicine has identified various factors influencing xerosis cutis. As we age, sebaceous gland function naturally declines, decreasing oil secretion, and the natural moisturizing factor that retains moisture also diminishes. External factors such as dry environments with low humidity, wind from air conditioners or heaters, hot showers, and cleansers with harsh detergents also damage the skin barrier. Endocrine diseases such as hypothyroidism, or chronic diseases such as diabetes, atopic dermatitis, and psoriasis, can worsen xerosis cutis as well.
What the Donguibogam calls body fluids can be understood in modern medicine as water, electrolytes, and extracellular matrix components such as hyaluronic acid and collagen. Blood supplies oxygen and nutrients to skin cells through microcirculation. The concept that the lung governs the skin suggests that immune responses and inflammation regulation related to lung health are closely linked to skin barrier function. In fact, respiratory system disorders often influence the cutaneous immune system, aggravating dryness or allergic reactions. Ultimately, dry skin is not merely a superficial issue, but the outcome of complex interactions both inside and outside the body.
