Overview
Urticaria pigmentosa is characterized by several to many brownish spots that itch and, when scratched, produce welts and reddened skin. The brown spots, seen here on the chest, contain mast cells with high levels of histamine. People sometimes develop generalized flushing and headaches from the massive histamine release from these spots.
Review Date 10/14/2024
Updated by: Elika Hoss, MD, Assistant Professor of Dermatology, Mayo Clinic, Scottsdale, AZ. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.