Number of cell layers of the stratum corneum in normal skin - relationship to the anatomical location on the body, age, sex and physical parameters.

We counted the number of cell layers in the stratum corneum (SC) of normal skin taken from different anatomical locations of the body of 301 individuals of various ages. Frozen 6 microm thick sections were stained with a 1% aqueous solution of safranin and observed under a microscope after application of 2% KOH solution. There were great variations in the number of SC cell layers (mean +/- SD) according to location and among different individuals. The smallest number was found in genital skin (6 +/- 2), followed in order by skin of the face (9 +/- 2), neck (10 +/- 2), scalp (12 +/- 2), trunk (13 +/- 4), extremities (15 +/- 4) and the palms and soles (47 +/- 24). The heel showed the largest number (86 +/- 36). No definite correlation was found between the number of corneocyte layers and sex of the individual, whereas there was a slight increase in the number of SC layers with age in the skin of the cheek and back, particularly in male individuals. Comparison of these data with those from functional assessments of the SC of the skin from various locations of healthy adults showed that transepidermal water loss, an indicator of SC barrier function, reflected the number of corneocyte cell layers. In contrast, high-frequency conductance, an indicator of the hydration state of the outer SC, did not seem to be under the influence simply of the number of SC cell layers.