With the first allergen contact the immune system creates IgE antibodies (sensitization). The IgE antibodies attach adhere to the surface of mast cells and basophils granulocytes. In case of a renewed contact with the allergen, these cells respond by releasing histamine and other substances which, in turn, cause anaphylaxis
Mast cells are part of the immune system and are present in every tissue of the body. Mast cells are responsible for the allergic reactions of the mucous membranes (red eyes, nasal symptoms, asthma, abdominal cramps, diarrhoea) or the skin (hives, known as urticaria).
The basophils granulocytes are white blood cells; they are present in the blood and react when larger amounts of allergens get into the bloodstream, e.g. after a bee sting or food intake. A strong reaction of basophils granulocytes affects the blood vessels; they expand, which can lead to a hypotension and circulatory shock. This maximum variation of allergic reaction called anaphylaxis.