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Related Concept Videos

Allergic Reactions: Anaphylaxis01:30

Allergic Reactions: Anaphylaxis

280
Anaphylaxis is a severe, life-threatening hypersensitivity reaction mediated by Immunoglobulin E (IgE) antibodies. When IgE binds to allergens, it triggers the release of mediators– histamine, leukotrienes, and prostaglandins from mast cells and basophils. These mediators cause vasodilation, edema, and inflammation, leading to various symptoms.The primary allergens causing anaphylaxis include food items (e.g., peanuts, shellfish), drugs (e.g., penicillin, asparaginase, corticotropin,...
280
Allergic Reactions02:06

Allergic Reactions

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Overview
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Drug Toxicity: Allergic Reactions01:30

Drug Toxicity: Allergic Reactions

209
Drug-related allergies are immune-mediated responses triggered by the administration of pharmacological agents. These hypersensitivity reactions are classified based on the immune mechanisms involved. The four primary types—Type I, II, III, and IV—are mediated by different immunological pathways and exhibit distinct clinical manifestations.Type I Hypersensitivity/ IgE-Mediated Reactions: Immunoglobulin E (IgE) immediately mediates Type I hypersensitivity reactions. Upon initial...
209
Hypersensitivity Reactions: Immune-Complex Reactions01:19

Hypersensitivity Reactions: Immune-Complex Reactions

269
Type III hypersensitivity reactions occur when antigen–antibody complexes form and activate the complement system. Normally, these complexes help the clearance of antigens by phagocytes and red blood cells. However, when large numbers of immune complexes are present, they can deposit in tissues—particularly in the walls of blood vessels—leading to inflammation and tissue injury. These deposits trigger complement activation and neutrophil recruitment, resulting in serum...
269
Hypersensitivity Reactions: Cytolytic Reactions01:01

Hypersensitivity Reactions: Cytolytic Reactions

208
Type II hypersensitivity involves IgG and IgM antibodies targeting cell surface antigens, leading to cell destruction. This can occur through complement activation, antibody-dependent cell-mediated cytotoxicity (ADCC), or acting as opsonins for phagocytosis. When excessive, these reactions cause significant tissue damage.Drug-induced hemolytic anemia is a common example, where drugs like penicillin or cephalosporins bind to red blood cells, forming drug-protein complexes. These complexes...
208
Hypersensitivities01:30

Hypersensitivities

7.3K
Hypersensitivity, also known as a hypersensitivity reaction or allergic reaction, is a condition where the body's immune system reacts abnormally to a foreign substance. Such substances, that cause hypersensitivity are referred to as an allergen, could be something typically harmless to most people, like pollen or certain foods.
Types of Hypersensitivities
Hypersensitivity reactions are categorized into four types: Type 1, Type 2, Type 3, and Type 4. Each type has a distinct mechanism...
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Related Experiment Video

Updated: May 1, 2026

Measuring Local Anaphylaxis in Mice
07:49

Measuring Local Anaphylaxis in Mice

Published on: October 14, 2014

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Biphasic anaphylactic reactions: occurrence and mortality.

M Rohacek1, H Edenhofer, A Bircher

  • 1Department of Emergency Medicine, University Hospital Basel, Basel, Switzerland.

Allergy
|April 15, 2014
PubMed
Summary

Biphasic anaphylactic reactions are rare and rarely clinically significant. This study suggests that prolonged monitoring after anaphylaxis resolution may not be necessary, as no deaths occurred.

Keywords:
anaphylaxisepidemiology

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Area of Science:

  • Allergy and Immunology
  • Emergency Medicine
  • Clinical Research

Background:

  • Anaphylaxis monitoring guidelines recommend observation after complete resolution.
  • The study aimed to assess biphasic reactions, ICU transfers, and mortality post-anaphylaxis.

Purpose of the Study:

  • To define the occurrence of biphasic and clinically important biphasic anaphylactic reactions.
  • To determine the frequency of intensive care unit (ICU) transfers due to anaphylaxis.
  • To ascertain mortality rates within 10 days of emergency department (ED) presentation for anaphylaxis.

Main Methods:

  • Retrospective analysis of clinical records from a tertiary care hospital's emergency department (ED).
  • Utilized hospital databases, direct patient/caregiver contact, and internet searches for mortality data.
  • Included 259,557 ED presentations over a 12-year period.

Main Results:

  • Anaphylaxis occurred in 0.20% of ED presentations (532 episodes).
  • Biphasic anaphylactic reactions were observed in 4.5% of cases (25 episodes), with 2.3% being clinically important.
  • No deaths were recorded within the 10-day follow-up period, regardless of monitoring duration.

Conclusions:

  • Clinically important biphasic anaphylactic reactions are uncommon.
  • Prolonged monitoring (≥8 hours) did not appear to impact outcomes or prevent mortality.
  • Findings support considering earlier discharge after complete anaphylaxis resolution.