612 � .5 = � -= Q Q ·s: � -= t .5 8 6 4 2 0 (i) 1 wt% SDS JOURNAL OF COSMETIC SCIENCE (ii) 1 wt% C12Ea (iii) In Vivo Control (iv) 10 wt% PG (v) 10 wt% G Figure 3. Transepidermal water loss (TEWL) values, with the error bars corresponding to standard errors, which were measured using an evaporimeter upon contacting human skin in vivo with aqueous contacting solutions i, ii, iv, and v, and for the in vivo control (iii). solutions (i and ii). There was a statistically significant difference in the deviation from baseline of TEWL values of skin treated with the two surfactant aqueous contacting solutions and that of skin treated with the two humectant aqueous contacting solutions (iv and v). These results indicate that the aqueous humectant solutions (iv and v) were not disruptive to the skin barrier. On the other hand, the aqueous surfactant solutions (i and ii) induce a statistically higher skin barrier perturbation relative to the untreated in vivo control (iii). The deviation from baseline of the visual skin dryness scores, determined by an expert grader as described in the Experimental section, are reported in Figure 4. The increases in skin dryness induced by the two aqueous surfactant solutions (i and ii) are signifi­ cantly higher than those corresponding to the in vivo control (iii)12 or to skin treated with the two aqueous humectant solutions (iv and v). 12 Note that the control for the in vivo skin barrier measurements is an untreated skin test site exhibiting natural skin hydration that is not occluded and is not exposed to aqueous contacting solutions i, ii, iv, and v. On the other hand, the control for the in vitro skin barrier measurements is a p-FTS sample that is exposed to PBS. The reason why the in vitro PBS control can be compared to the in vivo non-exposed, non-occluded control is discussed in the Experimental section.

1.2 .9 = � 0 0.8 � = .s = .t 0.6 e � 0 'fJJ. r'-l 0.4 � = 0.2 'fJJ. 0 ,... - "" "" RANKING OF SURFACTANT-HUMECTANT SYSTEMS 613 -- (I) 1 wt% SDS -- (ii) 1 wt% C12Ea -+- (ill) In Vivo Control ,......._.i - (iv) 10 wt% PG -..__ (v) 10 wt% G Figure 4. Visual skin dryness scores, with the error bars corresponding to standard errors, which were determined by an expert grader upon contacting human skin in vivo with aqueous contacting solutions i, ii, iv, and v, and for the in vivo control (iii). The expert grader could not discriminate differences in skin dryness between skin sites treated with the two aqueous humectant solutions (iv and v) or between skin sites treated with either of the two aqueous surfactant solutions (i and ii). These results indicate that the aqueous surfactant solutions (i and ii) induce skin dryness while the two aqueous humectant contacting solutions (iv and v) do not. One should note that in comparing results from the TEWL measurements and the visual skin dryness scores, the TEWL measurements more closely resemble the in vitro skin barrier perturbation measurements (skin electrical current and mannitol skin permeability) (see Figures 1-4) (17-20). In addition, an instrumental measurement like TEWL allows for finer discrimination between the effects of the aqueous humectant solutions (iv and v), and the in vivo control (iii), relative to the visual skin dryness scores determined by an expert grader. Indeed, there was no discrimination between the effects of the aqueous humectant solutions (iv and v) and the in vivo control (iii) (see Figure 4). Both the TEWL measurements and the visual skin dryness scores indicate that the aqueous surfactant solution containing 1 wt% C 12 E6 induces significant skin dryness relative to the in vivo control and to the aqueous humectant solutions (iv and v). This finding is consistent with in vivo studies that have shown that although nonionic surfactants like C 12 E6 do not induce significant erythema (skin redness) relative to SDS, they can be drying to the skin (21-24). This reflects the fact that nonionic surfactants like C 12 E6 can interact with the intercellular lipid bilayers