Immunoglobulin E (IgE) is responsible for most allergic reactions. Each type of IgE is specific to a particular allergen. When exposed to an allergen, IgE antibodies attach themselves to mast cells (normal body cells that produce histamines and other chemicals) or basophils. When exposed to the same allergen at a later time, the individual may experience an allergic response when the allergen binds to the antibodies attached to mast cells, causing the cells to release histamine and other inflammatory chemicals.