Various interventions for improving skin barrier function Original paper

As one of the largest organs in the body, the skin plays a protective immunological role. If the outermost layer, known as the skin barrier, does not function properly, foreign substances can enter the body and cause diseases such as atopic dermatitis (AD) and contact dermatitis.^[1] Skin barrier function is commonly measured using stratum corneum hydration (SCH) and transepidermal water loss (TEWL). Which supplements and topical interventions have shown promise in restoring skin barrier function?

This narrative review provided a general overview of the effects of prebiotics, probiotics, fatty acids, and other formulas on skin barrier function.

• Synbiotics. Galacto-oligosaccharides taken with probiotic milk for 4 weeks showed improved skin hydration and restored serum phenol levels.

• Probiotics. Topical application of Lactobacillus species (L. reuteri DSM 17937) decreased the production of inflammatory mediators and upregulated the gene for aquaporin 3, a skin barrier protein responsible for transporting water across cell membranes. Topical application of Lactobacillus rhamnosus was shown to improve the expression of loricrin and filaggrin, skin barrier proteins that are downregulated in AD. Oral Lactobacillus plantarum HY7714 increased skin hydration and TEWL after 12 weeks. Two months of oral Lactobacillus paracasei NCC2461 improved TEWL after tape stripping, a procedure that measures the quality of the stratum corneum. Four weeks of Lactococcus lacti H61 in milk increased skin hydration in both groups, compared to a probiotic yogurt, and the probiotic milk group also had a significant increase in sebum content.

• Prebiotics. Taking GOS for 12 weeks resulted in improvements in TEWL and skin hydration.

• Omega−3 fatty acids. Flaxseed oil was shown to improve TEWL, skin hydration, skin scaling, and roughness after 12 weeks of daily consumption. DHA for 8 weeks led to improvements in symptoms related to AD. Supplementing fish oil for 4 months led to a 30% improvement in clinical AD scores, but the comparison group given corn oil saw similar results.

• Gamma-linolenic acid. Clinical studies of evening primrose oil and borage oil have shown mixed results, but many have demonstrated beneficial effects on TEWL. Greater improvements in TEWL were seen in a subgroup with low baseline serum levels of a gamma-linolenic acid metabolite.

• L-histidine. Daily supplementation of L-histidine for 4 weeks significantly increased both filaggrin formation (a protein essential to the formation of the skin barrier) and skin barrier function and improved AD severity.