Transdermal
Transdermal — describing the movement of a substance across the skin and into the bloodstream, so that it acts on the body rather than only on the skin surface. In skincare the term is often used loosely, but true transdermal delivery is a specific pharmaceutical goal distinct from ordinary topical application.
Key points
- Transdermal delivery targets systemic circulation, as seen in medical patches for nicotine or hormones.
- Most cosmetic ingredients are intended to act on or within the skin, not to pass fully into the body.
- The stratum corneum is a strong barrier that limits how much of a substance can cross the skin.
- Molecule size, fat solubility, and concentration all influence how readily something penetrates skin.
Frequently asked
Are skincare products transdermal?
Most are considered topical rather than transdermal, because they are formulated to act on the skin's surface layers rather than to reach the bloodstream.
What makes an ingredient able to cross the skin?
Small, fat-soluble molecules tend to penetrate more easily, while large or highly water-loving molecules are largely held back by the outer skin barrier.
Related topics
This is a foundational entry in the SYNC Skin Encyclopedia and is expanded over time. Educational information only — not medical advice.
