Despite the efficacy of topical retinoic acid, skin reactions have limited its acceptance by patients. Other retinoids, like Retinyl
Palmitate (RP), are considerably less irritating, but they are also less effective. In order to enhance the performance of retinoids, in this
work RP has been added to cosmetic formulations such as nanoemulsions, which can provide better penetration of this active substance.
Because the vehicle can directly influence the skin penetration and the effectiveness of RP, two skin care products containing 5000 UI RP
have been developed and investigated, namely a nanoemulsifying system and a classic gel cream. In vitro penetration tests were conducted
by using Franz diffusion cells and placing porcine ear skin and iso-propanol in the receptor compartment. The RP concentration in
the skin layers was analyzed by high performance liquid chromatography, and a Zeta-Sizer system was employed for measurement of the
the particle size distribution. The penetration tests revealed a large difference between the vehicles in terms of the RP concentrations in
each skin layer. The classic gel cream furnished better RP penetration in both the stratum corneum and the epidermis without stratum
corneum + dermis, as compared to the self-nanoemulsifying system. The two vehicles displayed the same particle size (between 100 and
200 nm). Better understanding of RP skin delivery using different vehicles has been acquired, and the importance of evaluating the efficacy
of nanocosmetics. Results from the present study should also contribute to the assessment of commercial self-nanoemulsifying systems
with potential application in the facile production of nanoemulsions.