The effects of topical corticosteroids on delayed pressure urticaria

Six patients with delayed pressure urticaria (DPU) applied clobetasol propionate (0.05%) ointment or its base to predetermined test sites on the right and left thigh as part of a randomized, double-blind study. A pressure challenge was administered to each test site at the initial visit and repeated after 3 days and 6 weeks of treatment and at between 4 and 8 weeks after treatment. The areas of pressure-induced weals were measured 6 h after each challenge. At the 6-week visit, a 4-mm punch biopsy was taken from pressure-challenged skin on each test site. Sections were stained for mast cells and immunohistochemical labelling was used to demonstrate neutrophils (neutrophil elastase), eosinophils (eosinophil cationic protein), monocytes/macrophages (EBM 11), cells expressing the beta-2 integrins (CD11/18) and the vascular adhesion molecules, E selectin and intercellular adhesion molecule-1 (ICAM-1). In the steroid-treated sites, there was a significant decrease (P < 0.05, Wilcoxon's matched-pairs test) in the size of the pressure weals compared with baseline at 3 days, 6 weeks and at follow-up. Demonstrable mast cells were significantly decreased (P = 0.059) in the pressure-challenged areas in the steroid-treated sites compared with the base-treated sites. The histological response to pressure was minimal in both sites perhaps demonstrating an active pharmacological effect of the ointment base. In conclusion, the application of potent topical steroids significantly reduced the clinical response to pressure in patients with DPU, possibly through a reduction in mast cells.