Omega-6 (n-6) and omega-3 (n-3) fatty acids comprise the two classes of essential fatty acids (EFAs). The parent compounds of each class, linoleic acid (LA) and alpha-linolenic acid (ALA), give rise to longer chain derivatives that exert physiological effects in the skin. The skin lacks delta-6 and delta-5 desaturase enzymatic activity; thus, GLA, AA ,EPA, and DHA are also considered essential nutrients for the skin. Food sources rich in the various EFA metabolites are listed in green, shared enzymes are in blue, and EFA metabolites are in black. Modified from Figure 2 of 22.