Evaporimetiy in the differentiation of allergic, irritant and doubtful patch test reactions

The aim is to evaluate, using evaporimetry, the possibility of getting further information supporting clinical reading of allergic, irritant reactions and doubtful patch test reactions.

The investigation was carried out on 204 patients (182 female and 22 male, mean age 31.6 years), patch tested routinely as suspects of allergic contact dermatitis. We evaluated 326 reactions (203 allergic, 123 irritant or doubtful).

Mean values pf TEWL were: for the positive allergic reactions, 7.21 (SD, 2.26) at 48 h, 15.77 (SD, 5.50) at 72 h; and for the irritant or doubtful reactions, 7.55 (SD, 1.72) at 48 h, and 5.77 (SD, 1.41) at 72 h. TEWL in the 2 reactions groups at 72 h was significantly different (p<0.01).

The study shows (i) concordance between the evaporimeter values and the visual score; (ii) at 72 h, the evaporimeter values are increased in the allergic reactions but not in irritant or doubtful reactions; (iii) evaporimetry in the differential diagnoses of patch test reactions was deemed useful.