If you have an allergy, your immune system viewsthe allergen as an invader and chain reaction is initiated. White blood cellsof the immune system produce   g   antibodies. These antibodies attachedthemselves to special cells called mast cells, causing a release of potentchemicals such as histamine.  Thesechemicals cause symptoms such as –


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IgE is released to destroy the allergen and causesthe production of chemicals that trigger the allergic reaction.


One of these chemicals is called histamine.Histamine causes tightening of the muscles in the airways and the walls ofblood vessels. It also instructs the lining of nose to produce more mucus.


The most common allergens.


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Antigen – presenting cells, such as macrophages anddendritic cells that are present in the mucosal surfaces of the body, detectthe Allergen. This can occur in many ways, including inhalation into the noseand lungs through the skin and through the gastrointestinal tract.