Anaphylaxis

Anaphylaxis is a severe and rapid allergic systemic reaction to contact with an allergenic trigger substance (atopic or anaphylactic hypersensitivity). Minute amounts of trigger substances may cause a life-threatening anaphylactic reaction. Anaphylaxis may occur after ingestion, inhalation, skin contact or injection of a trigger substance. The most severe type of anaphylaxis is termed anaphylactic shock, which may lead to circulatory collapse and death.

Table of contents

1 Immediate Action 2 Symptoms 3 Causes 4 Treatment

Immediate Action

Anaphylactic shock is a life-threatening medical emergency because of rapid constriction of the airway, often within minutes of onset. Call for help immediately. First aid for anaphylactic shock consists of obtaining advanced medical care at once; rescue breathing (a skill which is part of CPR) is likely to be ineffective but should be attempted if the victim stops breathing. Look to see if a device such as an Epi-pen is available for administration of epinephrine by a layperson.

Symptoms

Symptoms can include respiratory symptoms, hypotension (low blood pressure), fainting, unconsciousness, urticaria (pruritic wheals), angioedema (swelling) and itching. The symptoms are related to the action of immunoglobulin E (IgE) which acts to release histamine and other mediator substances from mast cells. Histamine induces, beside other effects, vasodilation and bronchospasm (constriction of the airways).

Causes

Common causative agents in humans include food ingredients (nuts, peanuts, fruits), drugs (e.g. penicillin, contrast media, NSAIDs), latex, bee or wasp stings.

Treatment

Paramedic treatment in the field may include injection with epinephrine, administration of oxygen therapy and if necessary intubation during transport to advanced medical care.

The clinical teatment of anaphylaxis by a doctor and in the hospital setting aims at the cellular hypersensitivity reaction as well as at the symptoms. Antihistamine drugs (which inhibit the effects of histamine at histamine receptors) are usually not sufficient in anaphylaxis, and high doses of intravenous corticosteroids are often required. Hypotension is treated with intravenous fluids and sometimes vasoconstrictor drugs. For bronchospasm brochodilator drugs are used. In severe cases, immediate treatment with epinephrine may be lifesaving. Supportive care with mechanical ventilation may be required.