Pappas A, et al. - Experts evaluated the ceramide (CER) in the stratum corneum of healthy and acne skin and studied seasonal variation over the course of a year. Compared with healthy skin, lower ceramide levels reflected an increase in transepidermal water loss (TEWL) in acne which partly resolved in the summer. In acne skin, the individual ceramide species with 18 carbon 6 hydroxysphingosine (H) bases (including CER[N(24)H(18)], CER[N(26)H(18)], CER[A(24)H(18)], CER[A(26)H(18)]) were significantly reduced, suggesting that CER[NH] and CER[AH] species could be particularly important in a healthy skin barrier.