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Hypersensitivity
Anaphylaxis
Nafiseh Kiamanesh
Learning Objectives
• Knowledge of the mechanism which
causes anaphylaxis and the agents which
are most likely to cause it;
• be able to recognize the signs and
symptoms of anaphylaxis;
• Understand how to treat anaphylaxis
Lecture Objectives
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Definition
Introduction
Epidemiology
Pathophysiology
Aetiology
Diagnosis
Treatment
Prevention
What is anaphylaxis?
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Ana (without); phylaxis (protection / guard)
An acute systemic allergic reaction
Life-threatening
The result of a re-exposure to an antigen that elicits an
IgE mediated response
Usually caused by a common environmental protein
that is not intrinsically harmful
Often caused by medications, foods, and insect stings
It is a Type I hypersensitivity
True vs. pseudo anaphylaxis
4 Types of Hypersensitivity
• Type I : Mediated by IgE
• Type II : Mediated by anti-tissue Ab IgG
and IgM
• Type III : Mediated by immune complexes
• Type IV : Cell-mediated immune
complexes
History
Richet & Portier
Epidemiology
• Underreported
• 50/100 000 p/yr
• No known geographic, racial, or sex
predilection
• 1-15% at risk every year
• 1500 deaths p/yr
• Global increasing rates
Pathophysiology
Pseudoanaphylaxis
• Anaphylactoid Reactions are caused by
activation of mast cells and release of the
same mediators, but without the
involvement of IgE antibodies.
• Management is similar to anaphylaxis.
Primary Symptoms
• Time to onset is variable, but symptoms usually
occur within seconds to minutes of exposure to
the offending antigen.
CUTANEOUS
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Swelling (angio-oedema(
Urticaria
Redness (erythema)
Itching (pruritus)
RESPIRATORY
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Wheezing
Dyspnoea
Rhinitis
Laryngeal obstruction
causing stridor
Hypoxia
Secondary Symptoms
GASTROINTESTINAL
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Nausea
Diarrhoea
Abdominal Pain
Vomiting
CENTRAL NERVOUS SYSTEM
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CARIOVASCULAR
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Hypotension
 Tachycardia
 Arrhythmias
Confusion
Feeling of impending doom
Apprehension
Metallic Taste
Altered levels of consciousness
Death
• Death is usually attributable to
asphyxiation from upper airway edema
and congestion, irreversible shock, or a
combination of these factors. Death may
occur after many hours of shock from the
effects of the failure of other organs.
ANAPHYLAXIS
Causes
Anaphylaxis:
Foods
Peanuts
Tree nuts
Fish and shellfish
Soya products
Milk
Eggs
Insect stings
Bee venom
Wasp venom
Chemicals, drugs and other foreign proteins
Penicillin and other antibiotics
Intravenous anesthetic agents, e.g. suxamethonium,
propofol
Latex
Causes
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Anaphylactoid:
Opiates
Aspirin
Radio contrast media
Physical Exercise
Cold
Idiopathic:
No cause can be identified in 30% of patients
with anaphylaxis
Note
Any protein is a potential
allergen, which may cause an
anaphylactic reaction
Treatment
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Serum tryptase remains elevated for up to 6 hours
Immediate treatment with epinephrine
Anti-histamine
Others:
Corticosteroids
β2 agonist (inhaled)
Glucagon
IV fluids
Supplemental oxygen
prevention
• Avoidance of offending antigen, where
possible; skin testing and desensitization
to materials such as penicillin and
Hymenoptera venom, if necessary.
• Individuals should wear an informational
bracelet and have immediate access to
an unexpired epinephrine kit.
Epi-pen
Questions