Psychological stress can transiently perturb epidermal homeostasis through neuro-endocrine and inflammatory pathways, impacting hydration, desquamation, and barrier integrity. Here, we used an academic final-exam period as a real-life model of mild stress to track stress-responsive changes in corneocyte nanoscale morphology and to assess whether topical formulations can mitigate these effects. In a multi-week study with healthy student volunteers, corneocyte samples were collected longitudinally from treated sites (three cosmetic formulations) and matched untreated control areas. Atomic Force Microscopy (AFM) quantified nanoscale topography and extracted barrier-relevant descriptors.
During the exam period, untreated control sites showed a clear increase in the density of Circular Nano Objects (CNOs)—small nanoscale depressions previously associated with low Natural Moisturizing Factor (NMF) and reduced barrier integrity—along with higher surface heterogeneity. These patterns are consistent with stress-driven alterations in corneocyte maturation and barrier cohesion. In contrast, treated areas exhibited reduced CNO density and improved roughness/homogeneity parameters, suggesting a partial attenuation of stress-associated barrier impairment.