Film formation on the skin and subsequent occlusion effect was reported for lipid nanoparticles. It was found by Wissing et al., that the highest occlusion will be reached using low melting lipids, highly crystalline particles and very small particles. Nanoparticles have been found to be 15-folds more occlusive than microparticles. Particles smaller than 400 nm containing
at least 35% lipid of high cystallinity have been most effective (Fig. 4). Consequently Souto et al., found a higher occlusive factor for SLN in comparison to NLC of the same lipid content. Comparing NLC with different oil content led to the conclusion that an increase in oil content leads to a decrease of the occlusive factor.