A Study on the Induction of Hardening Phenomenon by Repeated Application of Sodium Lauryl Sulfate

Choi, Ji Hoon; Lee, Hee Bong; Park, Chang Kuen; Cho, Hee Jin; Park, Chun Wook; Lee, Cheol Heon

Abstract

BACKGROUND: Chronic irritant contact dermatitis, the common occupational dermatitis of the skin, could be caused by repetitive exposure of the skin to irritants. Adaptation of the skin to repeated influence of exogenous irritants is called the hardening. The defining characteristic of hardening phenomenon has been progressively decreasing inflammatory response with prolonged exposure to an irritant.
OBJECTIVE
The purpose of this study was to evaluate the induction of hardening phenomenon by the repeated application of various concentrated sodium lauryl sulfate (SLS) solutions.
METHODS
Once a day a 0.1%, 0.5%, 2% solution of SLS and distilled water were applied to the volar forearm skin in 15 healthy volunteers for 10 minutes over 3 weeks. After 3 weeks interval of rest, patch tests with 1% solution of SLS were conducted on previously irritated sites for 24 hours. We measured transepidermal water loss (TEWL) and erythema index (E-index) before irritation, during 3 weeks of repeated application. 4 days after the patches test, we measured TEWL and E-index once a day.
RESULTS
During 3 weeks of irritation with repeated application of 0.1%, 0.5%, 2% SLS solution, increase of TEWL was accelerated according to concentrations of SLS. In the study of 24-h patch test with 1% SLS solution on previously irritated sites after 3 weeks interval of rest, TEWL on distilled water application site was significantly higher than other sites irritated with SLS solution on D44 and D45. The TEWL values on the site irritated with higher concentration of SLS solution were lower than those with lower concentration of SLS solution. In contrast, there were no significant differences in E-index value during 3 weeks of irritation and after 24-h patch test with 1% SLS solution.
CONCLUSION
Hardening could be induced by repeated irritation with SLS solution for 3 weeks. We suggest that hardening could be induced more efficiently with the higher concentration of SLS solution than the lower concentration.