Allergies are an exaggerated immune response to foreign substances called allergens like pollen, molds, foods and medicines that cause symptoms like sneezing, itchy eyes, and wheezing. Allergies can be treated with medication, surgery or cold compresses. Antibodies are proteins produced by B cells that respond to stimuli like bacteria, parasites or transplanted organs to fight or neutralize them. Antibodies have a Y-shape and are made of two light and two heavy polypeptide chains. Antigens trigger antibody production and are then killed or neutralized; they include bacteria, pollen or proteins recognized as foreign by the immune system.