1. Skin structure
Epidermal layer (including stratum corneum and basal layer): The main functional layer of cosmetics, responsible for barrier protection and metabolism.
Dermis layer (containing collagen): directly related to the efficacy of anti-aging products.
2. Principles of use
Dry skin should focus on moisturizing (such as products containing hyaluronic acid), while oily skin should avoid excessive use of blocking ingredients (such as mineral oil).
Sunscreen products should pay attention to SPF/PA values to prevent UV accelerated photoaging
