However, this result appears not to be directly correlated to the in vitro accumulation of the drug in skin layers. Data reported in previous studies, in fact, indicate that the sodium deoxycholate gel is the formulation that provides the highest accumulation in the most superficial skin layers (Table 1). Reasonably, the high CP amount found in epidermis using Na-DOC gel is mainly located in the stratum corneum, and thus not available to elicit anti-inflammatory activity on the edema. This is plausible, considering the high lipophilicity of this molecule, characterized by a logP of 3.98 ± 0.61 (ACD/I-Labs, version 15.01, Advanced Chemistry Development, Inc., Toronto, ON, Canada, www.acdlabs.com, 2015). At the same time, the comparable CP levels found in the dermis for the three formulations (Table 1) cannot explain the superior in vivo performance evidenced by the formulation containing the chitosan/lecithin nanoparticles. However, these differences could be attributed to the fact that the in vitro situation is probably different from the in vivo situation, when inflammation and edema are present. In this case, in fact, the augmented capillary permeability can cause a higher CP absorption into the systemic circulation, resulting in a faster clearance from the inflammation site. In this context, nanoparticles can have a positive effect since they can accumulate inside the hair follicles, forming a drug reservoir less susceptible of fast drainage and clearance. Indeed, follicular accumulation of topically applied nanoparticles has been reported by many authors . Follicular accumulation of NP can take place in the hind paw model used here, since, contrarily to human palms and plants, which are hairless, Wistar rat foot pads contain hair follicles, although with a much lower density than normal rat skin .