Einfluß von Okklusionseffekten auf die Epikutantestung mit Natriumlaurylsulfat

When evaluating transepidermal water loss (TEWL) in patch testing we have to consider the occlusive effect of the patch as an important artificial impairment of the measurement. The aim of this study was to investigate the time course of these occlusion effects. Epicutaneous patches with SLS 0,25%, 0,5%, water and an empty test chamber (control) were applied on the volar forearm for different application intervals (12h, 24h, 48h). Test reactions were evaluated by measurement of TEWL immediately, every 15 minutes during the first hour, every 30 minutes during the following 3 hours and 24 hours after patch removal. Measurements immediately after patch removal showed a steep increase followed by a significant decrease in TEWL values. When compared to the basal TEWL values, TEWL values after SLS patch- testing remained increased for 24 hours, whereas TEWL values on water patch-sites were only significantly increased for up to 180 minutes, and on empty patch-sites only up to 120 minutes after patch removal. The prolonged increase of TEWL values in SLS patch testing seemed to be induced by barrier function damage caused by SLS itself as shown in various earlier studies. After the initial increase, TEWL values showed a significant decrease for all patches from 0 to 120 minutes after patch removal. Patch testing with water revealed a significant decrease in TEWL values up to 180 minutes, for empty chambers (control) up to 150 minutes after removal of patches. According to our data the occlusion effect on TEWL in patch testing will end 3 hours after removal of test chambers. We therefore recommend TEWL measurement in SLS patch testing after a period of at least 3 hours after patch removal. For practical purposes a 24 hour period after patch removal may be useful.