Skin reaction and recovery: a repeated sodium lauryl sulphate patch test vs. a 24-h patch test and tape stripping

Background Little is known of the predictive value of methods to test an individual's susceptibility to acquiring occupational contact dermatitis. Recently, the recovery rate after induced irritation was suggested for this purpose. Although it is likely that repeated exposure to sodium lauryl sulphate (SLS) is preferable to a single application, there is little evidence to support this idea. Similarly, little is known about whether the outcome of a repeated SLS test can be predicted by a brief test. Objectives We studied the relationship between the skin reaction after a repeated SLS test and two brief tests, devoting special attention to the recovery rate. Methods In 29 healthy volunteers, we measured transepidermal water loss (TEWL) and erythema after applying 0.03, 0.1 and 0.3% SLS for 6 h, 3 days per week, over a course of 3 weeks. The data were compared with the effects after applying 0.1, 0.3 and 1.0% SLS for 24 h and with 10 and 15 repetitions of tape stripping. Results A poor correlation was found between the repeated test and the brief SLS test, or tape stripping, when using an increase in TEWL (r = 0.04 and 0.26, respectively) or its recovery rate (r = - 0.01 and 0.42, respectively). Conclusions We presume that in a repeated test of sufficient duration, additional mechanisms come into play that are absent in a brief test, e.g. an alteration in the thickness of the epidermis, with a resulting change in the permeability of SLS. When such an effect differs between subjects it could explain the lack of agreement between the acute and the repeated tests. At present, a brief irritation test will, in all likelihood, be unable to assess an individual's susceptibility to occupational contact dermatitis