Atopy
Pathophysiology
In an allergic reaction, initial exposure to an otherwise harmless exogenous substance (known as an allergen) triggers the production of specific IgE antibodies by activated B cells. These IgE antibodies bind to the surface of mast cells via high-affinity IgE receptors, a step that is not itself associated with a clinical response. However, upon re-exposure, the allergen binds to membrane-bound IgE which activates the mast cells, releasing a variety of mediators. This type I hypersensitivity reaction is the basis of the symptoms of allergic reactions, which range from sneezing and rhinorrhoea to anaphylaxis. Allergens can be a number of different substances, for example pollen, dander, dust mites, foods.
Atopy-6