Trans-Epidermal Delivery
Trans-Epidermal Delivery — the process by which a topically applied ingredient moves across the outermost layers of the skin to reach deeper, living tissue where it can act. It describes how molecules navigate the stratum corneum barrier, and it depends heavily on an ingredient's size, solubility, and formulation.
Key points
- The stratum corneum is the main barrier that limits how much of an applied ingredient reaches the viable epidermis and dermis.
- Small, moderately lipophilic molecules generally penetrate more readily than large or highly water-soluble ones.
- Formulation factors such as pH, vehicle, and penetration enhancers can meaningfully influence how much active reaches its target.
- Most cosmetic ingredients act at or near the skin surface, and true delivery into deeper layers is limited by design for safety reasons.
Frequently asked
What limits how well an ingredient penetrates the skin?
Penetration is limited mainly by the stratum corneum, along with the ingredient's molecular size, water or oil solubility, and the formulation it is carried in.
Do all skincare ingredients need to penetrate deeply to work?
No, many ingredients such as occlusives, humectants, and UV filters work at or on the skin surface and are not meant to travel into deeper layers.
Related topics
This is a foundational entry in the SYNC Skin Encyclopedia and is expanded over time. Educational information only — not medical advice.
