On retinaldehyde, and why we stopped at 0.05%.
A short defense of the threshold dose.
There is a persistent confusion in skincare between higher numbers and better results. The data on retinoids does not support it. The dose at which collagen mRNA expression begins to increase is well below the dose at which the skin starts to flake — and the latter is not a sign of efficacy but of barrier disruption.
Retinaldehyde converts to retinoic acid in a single enzymatic step (retinol takes two). In Sorg’s controlled work it shows comparable efficacy to retinoic acid at one-tenth the irritation. 0.05% — encapsulated, in an emulsion that respects barrier lipids — is the dose at which we see consistent results without consistent complaint.
A higher number would sell better. It would also send a percentage of customers back to their dermatologist. We chose the dermatologist’s number.
