Characterization of irritant patch test reactions to topical D vitamins and all-trans retinoic acid in comparison with sodium lauryl sulphate. Evaluation by clinical scoring and multiparametric non-invasive measuring techniques.

The study was a single-centre, double-blind randomized, placebo-controlled within-subject comparison of 42 healthy volunteers. Occlusive patch test for 48 h was performed with solutions of 1 alpha,25(OH)2D3 (calcitriol), two vitamin D analogues (calcipotriol and KH 1060 (lexacalcitol)), all-trans retinoic acid and sodium lauryl sulphate (SLS) as reference irritant. Solution vehicles and an empty chamber was also included. Test evaluation was performed at day 2, day 3 and again on day 7. Test evaluation was based both on clinical scoring and on various non-invasive measuring methods. 1 alpha,25(OH)2D3, calcipotriol and KH 1060 all showed mild irritation in the concentrations tested. The number and severity of test reactions was found to be dose dependent based both on clinical scoring and on non-invasive measurements. Irritation of the vitamin D analogues mainly affected the vasculature with vasodilation and increased cutaneous blood flow. All-trans retinoic acid showed irritant reactions with some similarity to the tested vitamin D analogues; however, the reactions were more prolonged. Transepidermal water loss (TEWL) was affected neither after application of vitamin D analogues nor after application of all-trans retinoic acid and it was thus concluded that these substances are non-corrosive. SLS showed the known irritant mechanism with corrosion and increase in TEWL as the primary event.