Barrier recovery rate varies time-dependently in human skin

The recovery in cutaneous barrier functions, assessed in terms of transepidermal water loss, 1 h after tape stripping of volar forearm skin in human volunteers, was investigated at different times over the 24 h day. The barrier recovery rate was significantly lower between 20:00 h and 23:00 h than that at other time points. The skin surface temperature and the basal transepidermal water loss reached their highest values at about 03:00 h (33.6 degrees C and 0.30 mg cm-2 h-1), while the cortisol level in the saliva was highest at 09:00 h (7.8 pmol mL-1). These results suggest significant time-dependent variation in cutaneous barrier repair independent of changes in skin temperature and cortisol level.