Abstract

Dermal active substances, in particular anti-aging ingredients, find frequent use in cosmetics for their beneficial effects on the skin. But they can only have these effects if they are bioavailable. That means that the substance must efficiently penetrate the skin in a meaningful and effective concentration. Furthermore, the substance must be protected from degradation due to external influences such as light or oxygen, both as a raw material and in formulation. Retinol is a highly effective antioxidant and has long been known as an anti-aging ingredient. However, its chemical instability makes it a challenge for formulators. Furthermore, in high concentrations retinol causes skin irritation and redness. Retinol can be stabilised to a substantial degree by embedding it in a semi-crystalline, unordered matrix of selected solid and liquid lipids in the form of submicron particles in an aqueous suspension. This also gives efficient, controlled penetration of retinol from the particles into the skin over a prolonged period, minimising skin irritation. At the same time, with their effective adhesion to the skin, the lipid particles help restore the damaged skin barrier. This adhesive property also has the benefit of extending the release of retinol. The particles are in solid state at skin temperature and they are stabilised in suspension.