In skin, the physiological consequence of an ENaC-deficiency is not obvious directly at birth. Nevertheless, within hours after birth, mice deficient for the alpha subunit of the highly amiloride epithelial sodium channel (alphaENaC/Scnn1a) suffer from a significant increased dehydration. This is characterized by a loss of body weight (by 6% in 6 hours) and an increased transepidermal water loss, which is accompanied by a higher skin surface pH in one day-old pups. While early and late differentiation markers, as well as tight junction protein distribution and function seem not affected, deficiency of alphaENaC severely disturbs the stratum corneum lipid composition with decreased ceramide and cholesterol levels, and increased pro-barrier lipids, while covalently-bound lipids are drastically reduced. Ultrastructural analysis revealed morphological changes in the formation of intercellular lamellar lipids and the lamellar body secretion. Extracellular formation of the lamellar lipids proved to be abnormal in the knockouts. In conclusion, ENaC-deficiency results in progressive dehydration and consequently weight loss due to severe impairment of lipid formation and secretion. Our data demonstrate that ENaC expression is required for the postnatal maintenance of the epidermal barrier function but not for its generation.