Supplementary Material for: Monocentric, vehicle-controlled, double-blind study to assess the short- and long-term effects of a Ceramide NP C15-containing emollient on the skin microbiome and the skin barrier function in sensitive skin

Introduction:

Sensitive skin is a common skin condition that impairs quality of life and is characterised by unpleasant sensations to normally non-irritating stimuli. Restoration of skin barrier integrity can relieve symptoms, and accumulating evidence indicates a contributory role of the skin microbiome not only in barrier function but also as a potential modulator in sensitive skin. Ceramide-containing emollients improve barrier function and may modulate microbial communities via restoration of stratum corneum lipids, hydration, and immune regulation.

Methods:

In this randomized, double-blind, vehicle-controlled trial, an emollient containing Ceramide NP C15 was evaluated for its effects on sensitive skin symptoms and skin barrier function. Fifty participants applied the study products in a split-body design for six weeks. Primary assessments included skin physiology and symptom burden. Furthermore, skin microbiota changes were explored using flow cytometry (FC)-based bacterial profiling and 16s rRNA gene sequencing.

Results:

Both the Ceramide NP C15 formulation and the vehicle were associated with improvements in subjective symptoms. In participants with impaired skin barrier, treatment with the ceramide formulation was associated with a significant reduction in transepidermal water loss. FC- and 16S-based analyses indicated modest, treatment-associated changes in skin microbiota composition including an early and sustained increase in microbial evenness and a significant enrichment of Bifidobacterium.

Conclusion:

In this exploratory, randomized controlled study, a Ceramide NP C15-containing emollient was associated with improvements in skin barrier function. Exploratory microbiome analyses suggested treatment-associated changes in microbial community characteristics, which should prompt further investigations in their clinical relevance for sensitive skin.