Skin morphological changes, such as epidermal liquefaction, edema of collagen fibers and cell infiltration can be used as parameters to evaluate the possible damaging effects of the formulation. However, as already suggested by transepidermal water loss (TEWL) data, histological analysis of the rat skin did not reveal morphological tissue changes, at least after a single application of the formulations in this study. No cell infiltration signs were observed, and the structures of the stratum corneum, epidermis and dermis were preserved (Figure 4).