The influence of patch test size and design on the distribution of erythema induced by sodium lauryl sulfate

Patch testing is an invaluable tool for the experimental induction of acute irritant contact dermatitis (ICD), with a variety of chamber systems avail able for use. Ideally, the inflammatory reactions produced should be of uni form intensity across the test area, thereby facilitating grading of the re sponse and tissue sampling for histopathological studies. Unfortunately, an nular, follicular and/or blotchy erythema frequently occur. In this study, we set out to compare the performance of 5 patch test systems (8 mm, 12 mm and 18 mm Finn Chambers; 19 mm and 25 mm Hilltop chambers) when testing nor mal healthy volunteers with sodium lauryl sulfate at concentrations selecte d to produce mild, moderate and moderately severe reactions. Visual assessm ent of the patch test sites revealed good dose responses with all 5 chamber types. Uniformity of erythema across the test site was more closely linked to the actual intensity of response than the delivery system itself, mild reactions being far less likely to display homogeneous erythema than modera tely severe reactions. Extra large chambers did not perform significantly b etter than smaller chambers. Balancing the need for a uniform reaction patt ern and adequate tissue sampling area, against the exposure risk, we conclu de that 12 mm Finn Chambers represent the optimum patch test system for acu te SLS-induced irritation where histopathological investigations are the ul timate aim.