Mast cells release histamine when an allergen is encountered. The histamine response can produce sneezing, itching, hives and watery eyes.
Review Date 2/2/2020
Updated by: Stuart I. Henochowicz, MD, FACP, Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School, Washington, DC. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.