Ceramides are long chains of waxy lipids (fat molecules) that help in maintaining the structural integrity of the skin (skin barrier) & help in retaining moisture. Ceramides are found in high concentrations within the cell membrane of eukaryotic cells.
Free Radicals are unstable molecules (have an unpaired valence electron) that are released by UV light (sun) & air pollution. Free radicals damage the skin because they grab an extra electron (that they are missing) from atoms in the skin. This causes damage to the skin’s DNA and speeds up ageing process too. Using Antioxidants such as Vitamin A, Vitamin C and Vitamin E will avoid this damage by donating an electron to the free radical.