Abstract 1081 Poster Session II, Sunday, 5/2 (poster 26)

Preterm infants exhibit inadequate development of environmental interfaces such as the skin and lung. Recent reports indicate that postnatal application of topical emollients such as Aquaphor® may improve clinical outcome in preterm infants by augmenting barrier function. Application of topical agents to the skin of preterm infants may be analogous to the administration of pulmonary surfactant to the lung. Vernix caseosa is a naturally occurring biofilm which is absent in very low birth weight infants. In this study, we examined the effects of vernix, Aquaphor®, and petrolatum on skin barrier function. Vernix, Aquaphor®, and petrolatum were applied to the volar skin surface of adult volunteers following cleansing with fresh water. Surface electrical capacitance was measured as an index of surface hydration as described for preterm infants (Pediatrics 96(4):688,1995). Sorption-desorption profiles were performed to determine skin surface hydrophobicity as previously reported (Peds Res 35(4):443,1994). Particular attention was given to monitoring the acute (0-90 min) changes following vernix treatment in order to compare these effects with our earlier reports on the rate of skin surface drying in newborn infants following birth (Peds Res 43(4), 193A, 1998). Results: Following barrier cream application to freshly bathed human skin, surface hydration markedly increased over the vernix-treated site (v) but was unchanged over control (c), Aquaphor® (a) and petrolatum (p) treated sites: c = 100, *v = 364, a = 95, p = 93, reported as median capacitive reactance units (CRU;s); *p< 0.05). This significant difference persisted for 5 min after application c = 102 ± 4,* v = 121 ± 7, a = 99 ± 3 CRU's, mean ± sem, p< 0.05), but was absent at 90 min. Vernix treatment increased the rate of transepidermal water movement (TEWM) when measured 5 min after application c = 0.6 ± 0.1, *v = 1.7 ± 0.2, a = 0.1 ± 0.06, and p = 0.6 ± 0.3 CRU's/sec, mean ± SEM, *p<0.05). There were no observable differences in skin surface hydrophobicity as measured by the area under the curve of the sorption-desorption profiles. Conclusions: 1) These results indicate major differences between human vernix and oil-in-oil emulsions such as Aquaphor® and petrolatum. 2) Application of vernix to freshly bathed human skin results in immediate increases in surface hydration and TEWM followed by a return to baseline over 90 min. 3) In contrast, Aquaphor® and petrolatum evoke no change in these parameters compared to freshly bathed human skin. 4) The time course of drying following native vernix application parallels earlier reports of the rate of skin surface drying in term infants following birth. Speculation: We speculate that putative waterproofing effects of vernix in utero are secondary to its lipid components of probable sebaceous origin whereas its unexpected water binding/release properties are confined to detached fetal corneocytes embedded in the lipid matrix.

Funded by the National Institute of Nursing Research and the Skin Sciences Institute.