all allergic reactions are the result of the body's lymphocytes (white blood cells) encountering a foreign protein. even if this protein is harmless, an allergic person's immune system will begin producing antibodies and these go throughout the body, carrying with them histamine - used to help the body fight infection. however, an allergic person's body overproduces it in huge quantities. histamine in an allergic person will dilate surface blood vessels and depending on the allergen or part of the body exposed will produce the common symptoms.