1.Age: Children’s skin barrier function is not developed perfectly, and adults’ skin gradually ages after 25 years old, and the skin barrier function decreases, especially the sebaceous glands and keratin-forming cells of old people’s skin decline comprehensively, thus obviously affecting the barrier function. 2. Skin diseases: dermatitis and eczema can destroy sebaceous glands and epidermal stratum corneum due to inflammation of epidermis and scratching; psoriasis reduces lipid synthesis such as ceramide due to rapid formation of stratum corneum; congenital ichthyosis reduces protein content of epidermal keratin-forming cells, which decreases the quality of “bricks” and reduced secretion of “mortar” (natural moisturizing factor). Therefore, impaired skin barrier function may be the “result” of skin disorders or the “cause” of the development of the disease. 3.Drug or laser treatment: (1) Long-term topical hormones can destroy the barrier function of the skin in several ways. (2) Topical retinoids or other stimulating drugs can destroy the barrier function of the skin. (3) Cosmetic laser treatment, although it is an advanced and commonly used means of dermatological treatment and skin beauty in dermatology, has certain damage to the epidermal barrier function. (4) Bad life or care habits: such as excessive washing, exfoliating skin care, etc.