Anaphylaxis: Definition, Pathophysiology, Signs & Symptoms, Management in 4 steps

Anaphylaxis Symptoms

Anaphylaxis is an emergency situation, and can be life threatening within minutes, so early recognition and management is imperative


The term anaphylaxis was first used in 1902 by Richet and Portier to describe the reaction that occurred while they attempted to immunize dogs to a sea anemone toxin. Instead of providing prophylaxis, the injection induced a fatal hypersensitivity reaction, labeled anaphylaxis, the opposite of prophylaxis.


Anaphylaxis is a systemic hypersensitivity reaction caused by IgE-mediated immunologic release of mediators from mast cells and basophils. The release of preformed mediators such as histamine and newly formed mediators such as prostaglandins and leukotrienes increases vascular permeability, mucus secretion, vascular smooth muscle relaxation, and constriction of respiratory smooth muscle, leading to the clinical manifestations of anaphylaxis. Anaphylactoid or pseudo allergic reactions are similar to anaphylaxis; however, they are not mediated by an antigen–IgE antibody interaction. This type of reaction results from antigen acting directly on mast cell.

Anaphylactic Reaction
AnaphylaxisAnaphylactoid Reaction
it is a life-threatening clinical manifestationIt is clinically indistinguishable from anaphylaxis
IgE mediated immune hypersensitivity reaction involving
mast cell and basophil degranulation with the release of histamine, tryptase, prostaglandin and leukotrienes.
Not IgE mediated, Non Immune mediated, Direct mast cell degranulation
Causes of anaphylaxis
Food (nuts, eggs, fish, milk)
Insulin and other hormones,
Blood and blood products,
Insect bite/ snakebite,
Latex and allergy immunotherapy. 
Causes of Anaphylactoid reaction
NSAIDs( nonsteroidal anti-inflammatory drugs ),
radio contrast media,
Neuromuscular blocking agent,
Gama globulin,
Difference between Anaphylaxis & Anaphylactoid Reaction (Pseudo-allergy).

Signs and symptoms

Presentation of anaphylaxis
Presentation of anaphylaxis

Can present within minutes of exposure to allergen usually less than 1 hour after exposure, Rapid reaction on parenteral root first symptom is flushing, pruritus and sense of Doom.

Eye: Pruritus (itchy eyes), Lacrimation (watery eyes), Conjunctival erythema (redness of eye), Periorbital edema(Swelling around eyes).

Cardiovascular: Hypotension (abnormally low blood pressure), Tachycardia (an abnormally rapid heart rate), Arrhythmia(a condition in which the heart beats with an irregular or abnormal rhythm), Cardiac arrest(Sudden, unexpected loss of heart function, breathing and consciousness).

Gastrointestinal: Nausea, Vomiting, Diarrhoea, Abdominal pain.

Dermatological: Pruritis(itchy skin), flushing (skin becomes red and hot) , urticaria (a rash of round, red welts on the skin that itch intensely) , angioedema (Painless swelling under the skin, triggered by an allergen).

Respiratory: Dyspnea(difficult or laboured breathing), Stridor (a  harsh vibrating noise when breathing, caused by obstruction of the windpipe or larynx), Dysphagia (Difficulty swallowing), Pulmonary edema.

Neurological: Anxiety (a feeling of worry, nervousness, or unease about something with an uncertain outcome), Seizure [A seizure is a burst of uncontrolled electrical activity between brain cells (also called neurons or nerve cells) that causes temporary abnormalities in muscle tone or movements (stiffness, twitching or limpness), behaviors, sensations or states of awareness. Seizures are not all alike], Feeling of doom (is a sensation or impression that something tragic is about to occur.).

Emergency treatment is required for all the patient with significant respiratory, cardiac or gastrointestinal symptoms.


(A-B-C-D of Management)

Airway: Early intubation,

Cricothyroidotomy is a procedure that involves placing a tube through an incision in the cricothyroid membrane (CTM) to establish an airway for oxygenation and ventilation).

Breathing: Supplemental oxygen, initially using a nonrebreather mask at 15 liters/minute flow rate or commercial high flow oxygen masks (providing at least 70 percent and up to 100 percent oxygen) should be administered

Circulation: Secure 2 large IV cannula, attach cardiac monitor and give epinephrine stat (as early as possible).

Drug Epinephrine

Since it is a drug of choice and can be given via the following routes
Intramuscular (I.M)
Epinephrine 0.3 to 0.5 mg, 1:1000 to anterior or lateral thigh.

Intravenous (I.V)
Epinephrine 0.1 – 0.2mg (1ml) 1:1000 in 10ml 0.9% NaCl (0.1mg/ml) every 1-2min.

If patient response to epinephrine,
Treat all patients with histamine blockers (H1 & H2 blockers) like
Diphenhydramine(H1) 25-50mg IV,
Ranitidine (H2) 50mg IV

While if patient does not respond to epinephrine,
Glucagon 1-2 mg IV/IM every 5 minutes until effective.
For continued hypotension, continuous IV infusion at 0.1 microgram/kg/min titrated to effect and continuous aggressive fluid resuscitation.

In anaphylaxis, IV steroid has no role in acute phase but has role in preventing phase 2 reaction.
Once patient has stabilized and there is no known cause then referred the patient to an allergist for testing and monitoring and further management.

Author: Dr. Rabia
Dr Rabia Akhtar, MBBS(Bachelor of Medicine and Bachelor of Surgery), has perceived her graduation from India. Special Interest: Surgery, Chronic disease, Emergency Medicine, Paediatrics, Women's Health.
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