Dry skin may be caused by physical and chemical factors, age factors, seasonal factors, and may also be related to some diseases such as atopic dermatitis and hypothyroidism. 1. Physical and chemical factors: frequent bathing, sun exposure, etc. can lead to dry skin. Surfactants in detergents can cause loss of stratum corneum lipids and natural moisturizing factors during bathing, which can damage the skin barrier and cause dryness. Excessive sun exposure to ultraviolet light will change the metabolism of epidermal lipids, causing dry skin. 2. Age factor: with age, skin metabolism slows down, sebaceous gland secretion gradually becomes less, resulting in dry skin. 3. Seasonal factors: dry skin is seasonally related and occurs in winter. In winter, the climate is dry and the temperature changes drastically, so the skin is easy to dry. 4. Diseases: Dry skin can occur in atopic dermatitis, hypothyroidism, renal insufficiency and diabetes. When dry skin occurs, if you exclude physical and chemical factors, age factors, seasonal factors, you should consult a doctor in time to find out the cause of the disease and actively treat it.