If an allergen enters the body, your immune system triggers an antibody response. The antibodies bind to special cells, most importantly the mast cells. When the antibodies come in contact with the allergen, the mast cells release their own substances, including histamine. This causes unpleasant swelling and inflammation in the surrounding tissue - and it is your allergic reaction. When irritation remains localized in one area of the body, most symptoms are focused on the affected part of the body (for example, skin, airways, or eyes).
