Palmitoleic (16:1 n−7) Acid and Skin Health: Functional Roles and Opportunities for Topical and Oral Product Applications

Human skin lipids form interconnected pools that support barrier integrity, immune balance, and interactions with the environment. The stratum corneum barrier is built from an ordered mix of ceramides, cholesterol, and long-chain free fatty acids, while sebaceous lipids and their breakdown products shape surface properties and the skin microbiome. Hexadecenoic fatty acids are key at this interface. Palmitoleic acid (cis-9 16:1; 16:1 n−7, POA) is enriched in viable epidermis and remains detectable in stratum corneum lipids, whereas its isomer sapienic acid (cis-6 16:1; 16:1 n−10) predominates in human sebum. Together, they influence membrane organization, lipid fluidity, and antimicrobial defense. This mini-review outlines skin lipid composition and function with a focus on POA and then summarizes experimental and preclinical topical evidence suggesting antimicrobial effects, enhanced lubrication properties, protection from oxidative and ultraviolet B (UVB) injury, and enhanced wound repair. It also reviews early clinical findings from oral POA supplementation trials reporting improved hydration, barrier function, and markers of photo-oxidative aging, with exploratory signals for acne in a multi-nutrient regimen. Major POA sources include sea buckthorn pulp oil, macadamia and avocado oils, selected marine oils, ruminant fats, and emerging fermentation-derived products. Robust mechanistic human studies are still needed to define optimal dosing, formulations, and indications.