Ceramides are among the most important dermal sphingolipids, which are part of the skin’s own lipids. They account for about half of the lipids in the stratum corneum. Ceramides have numerous structural and biological functions in the human epidermis; for example, they play a role in preventing transepidermal water loss. In addition, ceramides regulate processes such as cell division and differentiation of keratinocytes. (1) Ceramides are classified according to the length of their bound fatty acid or the sphingoid backbone, for example, as AP, NP, or EOP ceramides.(1) A study found that the facial skin of patients with mild to moderate acne vulgaris contained a significantly lower percentage of ceramides and sphingosines, while transepidermal water loss was significantly higher compared to healthy control subjects.(2) In vitro studies also showed that phytosphingosine inhibits the growth of bacteria, including Cutibacterium acnes, and subsequent in vivo studies confirmed its antimicrobial properties through a significant reduction in the total bacterial count on unwashed hands.(1)