The Barrier, Ceramides, and the Things Nobody Should Promise
La Barrière Cutanée : Ce Qu’On Peut et Ne Peut Pas Promettre
Skincare does less than the advertising says and more than the sceptics believe. The line falls at the stratum corneum.
The stratum corneum is about twenty micrometres thick, built from dead corneocytes and the lipids packed between them. Within those lipids, ceramides, cholesterol and free fatty acids arrange themselves into lamellar sheets in roughly fixed proportion — and that is what people mean by the skin barrier. Almost everything skincare does, it does inside those twenty micrometres.
Proportion, not concentration
A common misreading is that more ceramide is better. In fact, raising the share of any single lipid on its own can disturb the packing of the lamellae. That is why a serious formula uses several structurally different ceramides together with phytosphingosine, rather than pushing one of them to a conspicuous number on the front of the box.
If the most expensive ingredient on a panel sits below the preservative, its role in the formula is mainly rhetorical.
Common sense among formulators
The verbs that should not appear
“Repair”, “rebuild”, “reverse” — in a cosmetic context all three cross a line. A cosmetic is legally defined as a product applied to the surface of the body to cleanse, protect or beautify; the moment it claims to have altered tissue structure or physiological function, it is no longer regulated as a cosmetic at all. This is not wordplay. It is an actual legal boundary.
Saying less does not make a product worse. Quite the opposite: an instruction leaflet willing to state plainly that a product acts on the stratum corneum is usually one written by somebody who has actually read the formula.
