Hives (urticaria) - close-up
Hives develop when histamine is released into the small blood vessels (capillaries). The capillaries dilate which causes a welt, and fluid oozes into the surrounding tissue, causing swelling. Histamine also causes intense itching.

Review Date:
10/23/2006
Reviewd By:
Kevin Berman, MD, PhD, Associate, Atlanta Center for Dermatologic Disease, Atlanta, GA. Review provided by VeriMed Healthcare Network.