OverviewMast cells release histamine when an allergen is encountered. The histamine response can produce sneezing, itching, hives and watery eyes.
Update Date 5/10/2014
Updated by: Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School, Washington, DC. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.