In fact, allergies are so common and cause so many medical and personal problems, that there is an entire governmental research institute devoted to the study of allergies. Each antibody molecule is capable of binding to a distinct three-dimensional molecular shape present on substances such as proteins or complex sugars, whether or not the substance is floating around freely, or whether the substance is an integral part of an organism. Thus, whenever a substance or complete organism invades our body, the immune system can respond to this intrusion by synthesis of antibodies. In the case of IgE, both the top and bottom parts of the antibody molecule can lead to problems for us. The receptor is located in the membrane of cells named mast cells and basophils.
Mast cells are all over the place within our skin, and basophils circulate within our bloodstream.
As IgE circulates, it may come in contact with mast cells or basophils, and through interaction with the receptor can specifically adhere to the membrane of these cells with the arms of the Y sticking out towards the surrounding environment, and the leg part of the molecule embedded within the membrane - would be analogous to you, standing with your feet and ankles sunk into wet cement, and your arms raised above your head. Now, if the substance against which the IgE was originally made appears and bumps into a mast cell or basophil within the skin or within the bloodstream respectively, the binding sites at the end of the arms of the IgE molecule may bind and hold onto the substance. This chemical can interact with other cell receptors specific for histamine, and trigger these cells to release other powerful substances as well. Now you know why we take anti-histamines to relieve these symptoms, and other chemicals to dry up our runny nose. All in all though, a mild reaction can simply be just a bother, and not particularly threatening.