In vivo barrier challenge and long‐term recovery in human facial skin

Recently, we developed a biophysical approach to characterize in vivo facial cheek skin as a function of stratum corneum (SC) depth, barrier function and during a 24‐h recovery period. The current study extends this work and characterizes the human facial cheek after barrier challenge and, for the first time, facial SC barrier recovery over a 4‐week period. Changes in the corneocyte size over the 4‐week recovery period, and correlations with changes in Trans‐Epidermal Water Loss (TEWL) were monitored. This approach allows complete characterization of SC barrier function after a full biological regeneration of the SC barrier following tape stripping. The structural and compositional changes in facial cheek were investigated using Attenuated Total Reflectance‐Fourier Transform Infra Red (ATR‐FTIR) spectroscopy, tape stripping, TEWL measurements and image analysis combined with optical microscopy to characterize the SC depth profile during the tape stripping stress and over 4‐week recovery period. TEWL increased significantly from baseline after sequential tape stripping. Corneocyte size decreased with successive tape stripping. An inverse direct correlation was determined between TEWL and corneocyte surface area. After 4 weeks, the corneocyte size and TEWL for the facial cheek recovered 100% from the tape stripping procedure. The in vivo ATR‐FTIR data demonstrated that lipid and sebum components on the surface of the facial cheek SC recovered within 24 h post tape stripping, whereas protein (Amide II) and water components recovered after 1 week.