Glycerin

Glycerin is the most proven humectant in dermatology — decades of research confirm it outperforms almost everything else at typical concentrations. As a component of the skin’s Natural Moisturising Factor it draws water into the stratum corneum, and uniquely it also facilitates lipid bilayer organisation in dry skin, repairing barrier structure from within. At 2–10% it reduces tightness, flaking, and roughness within hours. Glycerin is non-greasy, non-comedogenic, virtually non-irritating, and stabilises other ingredients. Its only limitation is a tacky feel at very high concentrations, which skilled formulation avoids. No routine is complete without it: it is the quiet workhorse hiding in almost every effective moisturiser on earth.