This article waslast modified on July 10, 2017.
A type of tissue cell found throughout the body but especially in connective tissue such as the skin, lining of the intestine and air passages as well as in the bone marrow. Mast cells contain granules that store chemicals. These chemicals are released as part of the body's normal response to injury but also may be released as part of an allergic response to exposure to an allergen. The chemicals that are released can cause the allergic signs and symptoms.