Oral Colloidal Silicon Dioxide Added to Routine Treatment for Acute Urticaria in the Emergency Department

The goal of this observational study is to learn whether adding a single oral dose of colloidal silicon dioxide, an enterosorbent, to routine emergency department treatment is associated with faster early improvement in adults with acute urticaria. The main question it aims to answer is: Is the change in urticaria activity over the first 2 hours different in patients who receive colloidal silicon dioxide in addition to intravenous pheniramine compared with patients who receive intravenous pheniramine alone? Treatment is chosen by the treating emergency physician as part of routine care, before patients are approached for the study. Participants are assessed before treatment and at 1 and 2 hours, and are contacted by telephone at 24 hours.