Anaphylaxis or anaphylactic reaction is a term reserved for a serious and immediate hypersensitivity reaction that can be allergic or non-allergic. It is defined by a combination of signs and symptoms affecting at least two organs. Anaphylactic shock is the most severe expression of this because it can be fatal. A drop in blood pressure defines anaphylactic shock. Anaphylaxis is caused by the release of mediators, usually triggered by antigens binding to membrane-bound specific IgE. The increase in the prevalence of food allergies over recent decades has resulted in a very significant rise in the frequency of these anaphylactic-type allergic reactions. Foods along with drugs (muscle relaxants, antibiotics) are the two allergens that are the leading causes of anaphylaxis, ahead of hymenoptera venoms (wasps and bees). However, in some cases sudden mast cell degranulation can be caused by physical factors, for instance in cold urticaria, or by drugs, without specific IgE being involved. This is known as an anaphylactoid reaction. Irrespective of the mechanism involved or the causative agent (food, drug or protein), the therapeutic management of anaphylactic shock is always the same and adrenaline is the cornerstone of treatment.

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Allergy/Asthma Information Association

World Allergy Organization