Reproducibility of irritant patch test reactions to sodium lauryl sulfate in a double-blind placebo-controlled randomized study using clinical scoring - Results from a study group of the German Contact Dermatitis Research Group (Deutsche Kontaktallergie-Gruppe, DKG)

Reading of doubtful patch test reactions can be improved by comparing them to defined negative, allergic and irritant controls. For the latter, an irr itant patch test is needed that gives sufficiently reproducible results. In our double-blind, placebo-controlled. randomized study, we have analysed t he synchronous reproducibility of patch tests with 0%, 0.0625%, 0.125%, 0.2 5%, 0.5% and 1.0% sodium lauryl sulfate (SLS). Tests and readings were done according to ESCD guidelines. 139 patients (75 women, 64 men) 18 to 77 yea rs old were tested. The % of positive patients as well as the % of reproduc ible positive reactions increased with rising concentrations of SLS to a ma ximum of approximately 90% and 85%, respectively with 1 % SLS. Time courses of reactions were also related to the concentration of SLS: with 1 % SLS, plateau-type time courses were most common (65%), followed by decrescendo- (23%) and crescendo-type reactions (12%). With 1% SLS, very similar mild to moderate reactions were obtained on days 2 and 3. The reaction threshold a nd reproducibility of tests were not related to age and sex of patients or to their own assessment of skin irritability. We conclude that 1% SLS is ap propriate for an irritant patch test that gives sufficiently reproducible r esults.