Variation in barrier impairment and inflammation of human skin as determined by sodium lauryl sulphate penetration rate

Background Skin irritability after a brief exposure to the model skin irritant, sodium lauryl sulphate (SLS), is known to vary considerably between individuals. A difference in the skin barrier to SLS may contribute to this variation. To date, no human in vivo data have been available on SLS penetration into the skin. Objectives We studied whether the SLS penetration rate into the stratum corneum (SC) is related to impairment of the water barrier function and inflammation of the skin. Methods The penetration of SLS into the SC was assessed using a noninvasive tape-stripping procedure in 20 volunteers after a 4-h exposure to 1% SLS. Additionally, the effect of a 24-h exposure to 1% SLS on the skin water barrier function was assessed by measuring the transepidermal water loss (TEWL). The accompanying inflammation was quantified by measuring erythema. Results The mean +/- SD diffusivity of SLS (D) and the SLS permeability coefficient (K-p) were 1.4 +/- 0.6 x 10(-8) cm(2) h(-1) and 1.5 +/- 0.7 x 10(-3) cm h(-1), respectively. A multiple regression analysis showed that the baseline TEWL, SC thickness and SLS penetration parameters K (SC/water partition coefficient) and D clearly influenced the increase in TEWL after the 24-h irritation test (explained variance: r(2) = 0.80). Change in erythema was mainly influenced by SC thickness. Conclusions We found that variation in the barrier impairment and inflammation of human skin depends on the SLS penetration rate, which was mainly determined by SC thickness.