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Infants of less than 32 wk gestation have a defective epidermal barrier, with increased skin permeability and transepidermal water loss (TEWL). We studied the effect of a nonadhesive semipermeable dressing on the epidermal barrier of premature infants and on fetal skin transplanted to nude mice. Fifteen infants with a mean estimated gestational age of 27.7 wk and 16 human fetal skin grafts (estimated gestational age, 23-26 wk) transplanted to eight nude mice were studied. One lower leg (or skin graft) was treated and the other left untreated as a control. In the infants, TEWL was measured on control skin and treated skin (both through the dressing and after temporary dressing removal) on d 0, 1, 2,4, and 7. Bacterial and fungal cultures were also performed. In the mice, TEWL and skin blood flow were measured on d 0, 2, and 4. Biopsies were obtained on d 4 for a cell proliferation assay, histology, and electron microscopy. Treated infant skin showed a consistently lower bacterial number and a significantly decreased TEWL (measured through the dressing). There was also a significantly lower TEWL on the treated side, measured after temporary dressing removal, on d 1, 2, 4, and 7, documenting improved epidermal barrier function. The animal study revealed decreased TEWL and a nearly 2-fold greater d-4 keratinocyte proliferation (p = 0.01) in treated skin and decreased blood flow on d 4 in control skin (p = 0.01). There was no significant difference in the volume density of membrane coating granules or the morphology of intercorneocyte spaces. It is concluded that semipermeable dressings improve epidermal barrier function without increasing bacterial or fungal colonization in premature infants, and that increased cellular proliferation is associated with improved barrier function in semipermeable dressing-treated fetal skin. The T E W L of the premature infant decreases a s the child ages. Harpin and Rutter (3) examined barrier properties in infants of 25 t o 41 w k gestation. They evaluated T E W L and blanching response t o phenylephrine. Their results demonstrated that earlier gestational age infants had greater skin permeability t o phenylephrine a n d greater T E W L . In the premature infants less than 32 w k E G A w h o survived the initial course, there w a s a rapid epidermal barrier maturation such that b y 2 w k of postnatal age they had skin permeability a n d T E W L nearly equivalent to values found in mature infants (3).Occlusive dressings accelerate wound healing, a property recognized since 1962, when Winter (5) demonstrated an accelerated rate of reepithelialization in superficial w o u n d s in s w i n e t h a t w e r e t r e a t e d w i t h a polyethylene film. Many different synthetic occlusive

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