Skin barrier properties and possible skin irritation and skin damage induced by the formulation applied can be assessed by transepidermal water loss (TEWL) measurements  and histology. In fact, it has been shown that, in rat skin, TEWL increase is directly correlated to barrier function impairment produced by irritants. In particular, sodium lauryl sulfate exposure increased TEWL approximately 8 times compared to the control value (10.3 g·m−2·h−1) . Typical basal values of TEWL obtained in the present work were in the order 11.1–12.6 g·m−2·h−1, close to the literature data reported before. The TEWL value of rat skin is typically higher than the value of human skin (5–6 g·m−2·h−1), probably due to the high density of hair follicles in rat skin .