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An abnormal, acquired reaction to a foreign antigen. The antigen may make skin contact, be inhaled, ingested or injected. It is characterized by degranulation of mast cells, which had been sensitized by previous exposure to the same antigen, with consequent release of mediators such as histamine, leukotriene and prostaglandin. These produce principally smooth muscle contraction and vasodilation.
The reaction may vary from mild local irritation to anaphylactic shock and possible death
Desensitisation has in the past been popular, became unpopular after a small number of deaths, and is now becoming more widely considered.
Allergy is an area infested by quacks and quackery.
Common and potentially potent allergens include: