Technically Speaking: SPF in Relation to Sunscreen Application In Vivo

September 28, 2007 | Contact Author | By: Charles Fox, Independent Consultant
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Skin and Skin Care
Intercellular lipids in moisturizer: Sano et al. review the development of skin moisturizers using intercellular lipid technology. The stratum corneum (SC) consists of corneocyte cells and intercellular lipid layers that are located between corneocyte cells. The intercellular lipid layers are considered important to barrier protection and water-holding capabilities.

Intercellular lipid layers, consisting of ceramide, cholesterol and fatty acid, form a lamellar structure to hold water in its hydrophilic moiety. The authors developed pseudo-ceramides to optimize water-holding properties of the natural ceramides. They reportedly found that a sphingosine/ceramide/water system formed intercellular lipidlike structures and that the emulsion incorporating this system showed significant improvement on skin roughness and water-holding properties in skin.

Plant ceramides in oral, percutaneous applications: Asia et al have evaluated the skin moisturizing effects of plant ceramides via oral and percutaneous routes.2 This study also was undertaken to evaluate the assay performance of two methods for measuring the water-holding capacity of the skin—one that measures water content in the stratum corneuma and the other that measures transepidermal water loss (TEWL).

The investigators studied the effects of newly developed skin moisturizers made of plant ceramides with both assays. The within-run as well as day-to-day reproducibility of both methods were found to be satisfactory. When rice-derived NIPPN ceramide RC was used topically for three weeks by 23 healthy volunteers, the water content in the SC of the leg was significantly increased to 141% of the baseline value, in comparison with the after-placebo use (111%) (p <0.05); and the TEWL was significantly suppressed to 23% of the baseline, in comparison with that after-placebo use (39%) (p <0.01).

When 20 mg or 40 mg/day of corn-derived NIPPN ceramide CP was administered orally for three weeks, the water content in the SC of the leg was significantly increase to 290% and 394% of the baseline value, respectively, in comparison with the after-placebo administration (141%) (p <0.05); and the TEWL was suppressed to 33% and 14% (p <0.05) of the baseline values, respectively, in comparison with the after-placebo administration (69%). This data by both methodsa,b suggests that the two plant ceramides are promising as skin-moisturizing agents and not only for topical application, but also for oral ingestion.

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