Nanoemulsions: a new vehicle for skincare products

Nanoemulsions consist in very fine oil-in-water dispersions, having droplet diameter smaller than 100 nm. Compared to microemulsions, they are in a metastable state, and their structure depends on the history of the system. In the present work, nanoemulsions were prepared with a high shear device, which is less constraining than spontaneous emulsification procedures. Nanoemulsions are very fragile systems by nature. As they are transparent, the slightest sign of destabilisation appears visually. Two major sources of unstability were identified and extensively studied: Ostwald ripening and depletion induced floculation following the addition of thickening polymers. The control of these two mechanisms allowed the industrial production of a large variety of cosmetic products, from water-like fluids, to ringing gels obtained by increasing the oil phase content or by adding polymers. The nanoemulsions are easily valued in skin care due to their good sensorial properties (rapid penetration, merging textures) and their biophysical properties (especially their hydrating power).