These red (erythematous), hive-like (urticarial) spots (plaques) are caused by inflammation of the blood vessels (urticarial vasculitis) and do not change over a 24-hour period. They may or may not turn white (blanch) with pressure.
Review Date 4/8/2019
Updated by: Gordon A. Starkebaum, MD, MACR, ABIM Board Certified in Rheumatology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.