An Allergic Reaction occurs when the immune system overreacts to a harmless substance known as an allergen. The immune system protects the body from infections, viruses, and diseases. In some people, substances such as pollen, certain foods, latex, molds, pet dander, dust mites, or insects’ stings are allergens that trigger the production of antibodies called immunoglobulin. These antibodies travel to cells that release chemicals causing symptoms most often in the nose, lungs, throat, sinuses, ears, lining of the stomach or the skin.