What is anaphylaxis?
Anaphylaxis or anaphylactic shock is an acute, rapid and severe allergic reaction caused by a sudden release of histamine from white blood cells including mast cells and basophils. Histamine is involved in allergic reactions and binds to receptors in small blood vessels causing them to dilate and widen, which allows leakage of fluid into the surrounding tissues, causing swelling. Anaphylaxis is induced by an allergen, which is a substance that the immune system reacts to as a potential threat, most commonly foods like peanuts, shellfish and eggs; a bee or wasp sting, and latex; also some medicines like aspirin and penicillin. It can be life-threatening if not treated rapidly, with symptoms including drop in blood pressure, increased heart rate, difficulty breathing and wheezing due to bronchospasm (narrowing of the airways), swelling of the throat, tongue and face. Anaphylaxis does not usually occur on the first exposure. For example, the first bee sting sensitises the immune system resulting in a stronger allergic reaction with the next sting and increasing risk of anaphylaxis.
Emergency treatment for anaphylaxisAdrenaline (or epinephrine) is a naturally occurring hormone produced by the adrenal gland and also by certain nerve cells and is released in response to stress. It causes constriction and narrowing of blood vessels, increased heart rate and widening of the air passages, all of which under normal conditions contribute to preparation for the “fight or flight” response.
Adrenaline is used for emergency treatment of acute anaphylaxis and works by binding to specific adrenergic receptors on blood vessels walls causing them to constrict and become less permeable; also on bronchial smooth muscle of the airways, causing them to relax and widen, which helps return breathing to normal; and on the heart, which helps return heart beat to normal, as well as increasing blood pressure. When injected as soon as possible after exposure to the allergen, adrenaline can relieve life-threatening symptoms.