Oils are lipids. The lipids present in our skin, the sebum and the epidermal lipids1 come from two very different sources.
The sebum is produced and secreted by the sebaceous glands onto the surface of our skin. The sebaceous glands are located in the dermis where it is usually found in association with hair follicles, forming the pilosebaceous unit. Sebum is a complex mixture of lipids: 57.5% tryglycerides and their hydrolysis products, 26.0% wax esters, 12.0% squalene, 3.0% cholesterol esters and 1.5% cholesterol2. Among these, squalene and wax esters are unique to human sebum and not found anywhere else in the body nor among the epidermal lipids3-4-5-6.
The epidermal lipids are comprised of 50% ceramides, 25% cholesterol, 15% of free fatty acids7 as well as smaller amounts of cholesterol esters and cholesterol sulfate8. Epidermal lipids are secreted by the cells of the epidermis called keratinocytes. As keratinocytes journey from the basal compartment of the epidermis (where they are born) towards the outer layers of the skin to die and shed off as scales, they must differentiate and undergo extensive physical and chemical changes. In their last step of differentiation in the outermost layer of the skin (stratum corneum) they release lipids (lamellar granules) into the spaces between the cells. These lipid packages fill in these spaces between the cells to act like mortar or cement, ensuring the skin barrier function9-10-11. This layer of lipids is our environmental shield barrier, protecting against the external elements and maintaining the internal environment intact. In contrast to free-flowing oils that make up sebum, the epidermal lipids are in a solid state at room temperature.
Oils have been shown to help maintain and repair the integrity of the lipid barrier, by inhibiting oxidative damage, known to be one of the primary cause of wrinkles12-13. Facial oils can be suitable for all skin types and are known to provide hydration in moisture depleted mature skin.
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- Strauss JS, Pochi PE, Downing DT: Skin lipids and acne. Annu Rev Med 1975; 26: 27–32, Picardo M, Ottaviani M, Camera E, Mastrofrancesco A: Sebaceous gland lipids. Dermatoendocrinol 2009; 1: 68–71
- Pappas A: Epidermal surface lipids. Dermatoendocrinol 2009; 1: 72–76
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- Smith RN, Braue A, Varigos GA, Mann NJ:The effect of a low glycemic load diet on acne vulgaris and the fatty acid composition of skin surface triglycerides. J Dermatol Sci 2008; 50: 41–52
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- Dwoning DT, Stewart ME, Wertz PW, Colton SW 6th, Strauss JS. Skin lipids. Comp Biochem Physiol B. 1983; 76;673-8
- Strauss JS, Pchi PE, Downing DT: Skin lipids and acne. Annu Rev Med 1975; 26:27-32
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- Darmstadt GL1, Saha SK, Ahmed AS et al. Effect of topical treatment with skin barrier-enhancing emollients on nosocomial infections in preterm infants in Bangladesh: a randomised controlled trial. Lancet. 2005; 365:1039-1045
- Darmstadt GL1, Saha SK, Ahmed AS, et al. Pediatrics. Effect of skin barrier therapy on neonatal mortality rates in preterm infants in Bangladesh: a randomized, controlled, clinical trial. 2008; 121:522-529