Your immune system controls how your body defends itself. For instance, if you have an allergy to dust mites, your immune system identifies dust mites as an invader or allergen. Your immune system overreacts by producing allergic antibodies called Immunoglobulin E (IgE). These antibodies travel to cells that release chemicals, causing an allergic reaction. This reaction usually causes symptoms such as sneezing, stuffiness, a runny nose, or itchiness in your nose, the roof of your mouth, throat, eyes or ears.