• ceramides;
  • lipids;
  • membranes;
  • skin;
  • sphingolipids


Sphingolipids are crucial for the life of the cell. In land-dwelling mammals, they are equally important outside the cell—in the extracellular space of the skin barrier—because they prevent loss of water. Although a large body of research has elucidated many of the functions of sphingolipids, their extensive structural diversity remains intriguing. A new class of sphingolipids based on 6-hydroxylated sphingosine has recently been identified in human skin. Abnormal levels of these 6-hydroxylated ceramides have repeatedly been observed in atopic dermatitis; however, neither the biosynthesis nor the roles of these unique ceramide subclasses have been established in the human body. In this Minireview, we summarize the current knowledge of 6-hydroxyceramides, including their discovery, structure, stereochemistry, occurrence in healthy and diseased human epidermis, and synthetic approaches to 6-hydroxysphingosine and related ceramides.