Local allergic reactions can occur for a variety of reasons and can pose a formidable challenge with respect to identifying the cause.

Allergic reactions are complicated and somewhat unpredictable events that are triggered by various environmental factors or other physiologic abnormalities. There are several special cells and blood proteins that mediate most allergic reactions. Of the immune proteins (IgG, IgE, and so on), Immunoglobulin "E" is the one most often involved with allergic reactions. There are several special cells in the body that play a role in allergic reactions: the "mast" cell and the "eosinophil." The eosinophil is a white blood cell that looks like a giant raspberry when viewed under the microscope. The mast cell resides mostly in various body tissues