Hypersensitivity Types and Anaphylaxis Response
Key Points
- Hypersensitivity reactions are exaggerated immune responses to antigens that can damage healthy tissue.
- Allergic responses are hypersensitivity reactions to allergens that are usually harmless to most people.
- Type I reactions can progress rapidly to anaphylaxis with airway and circulation compromise.
- Immediate recognition and epinephrine-first treatment are core nursing safety priorities in severe reactions.
Pathophysiology
Hypersensitivity occurs when immune activation is excessive, prolonged, or directed at inappropriate targets. Instead of resolving threat safely, inflammatory mediators and immune-cell activity produce tissue injury and systemic symptoms.
Mechanisms vary by reaction type, including IgE-mediated mediator release, antibody-mediated cytotoxicity, immune-complex deposition, delayed T-cell reactions, and autoimmune self-targeting. Clinical impact ranges from mild discomfort to life-threatening cardiopulmonary compromise.
Classification
- Type I (Immediate): IgE-mediated mast-cell and basophil activation; may cause urticaria, bronchoconstriction, and anaphylaxis.
- Type II (Cytotoxic): IgG/IgM antibodies target cell-surface antigens and trigger cell destruction (for example hemolytic transfusion reactions and autoimmune hemolytic anemia).
- Type III (Immune Complex): Antigen-antibody complex deposition causes local inflammation and tissue damage (for example post-streptococcal glomerulonephritis, serum sickness, and systemic lupus erythematosus).
- Type IV (Delayed): T-cell mediated inflammatory response with delayed tissue injury (for example contact dermatitis and tuberculin skin-test reactions).
- Type V (Autoimmune/Stimulated): Autoimmune self-antigen targeting with chronic inflammatory tissue damage (for example rheumatoid arthritis, multiple sclerosis, and type 1 diabetes).
Nursing Assessment
NCLEX Focus
Prioritize airway, breathing, and circulation signs first when severe allergic symptoms evolve quickly.
- Assess for early allergic findings such as itching, sneezing, hives, congestion, and rhinorrhea.
- Assess for anaphylaxis red flags: dyspnea, bronchoconstriction, angioedema (especially around eyes, lips, and throat), generalized urticaria, and airway swelling.
- Assess for escalating severe-reaction cues, including apprehension or a sense of impending doom.
- Monitor for hemodynamic compromise including widespread vasodilation and reduced perfusion.
- Trend vital signs and respiratory effort continuously during acute reactions.
Nursing Interventions
- Stay with the client and initiate continuous monitoring during suspected anaphylaxis.
- Stabilize or support airway and administer supplemental oxygen as needed.
- Administer intramuscular epinephrine (1:1000) first line at 0.3-0.5 mL as prescribed.
- Administer adjunct therapies (antihistamines, beta-agonist such as albuterol, corticosteroids) per orders.
- Prepare additional supportive measures, including IV fluids, based on evolving instability.
- Educate client/family on trigger avoidance, emergency action planning, and epinephrine auto-injector use when indicated.
Time-Critical Emergency
Delayed treatment of anaphylaxis can rapidly progress to airway obstruction, cardiovascular collapse, and death.
Pharmacology
| Drug Class | Examples | Key Nursing Considerations |
|---|---|---|
| epinephrine | IM epinephrine 1:1000 | First-line treatment in anaphylaxis; give promptly. |
| antihistamines | class-based agents | Adjunct symptom control for pruritus and urticaria. |
| corticosteroids | class-based agents | Reduce inflammation and risk of delayed recurrence. |
Clinical Judgment Application
Clinical Scenario
A client develops generalized itching, facial swelling, wheezing, and worsening dyspnea minutes after exposure to a known allergen.
- Recognize Cues: Rapid multisystem allergic findings with airway risk.
- Analyze Cues: Type I hypersensitivity has escalated to probable anaphylaxis.
- Prioritize Hypotheses: Highest priority is impending airway compromise and circulatory instability.
- Generate Solutions: Immediate epinephrine-first emergency pathway with airway and oxygen support.
- Take Action: Administer epinephrine, monitor continuously, and implement ordered adjunct therapies.
- Evaluate Outcomes: Improved breathing, reduced edema, and stabilized perfusion parameters.
Related Concepts
- anaphylaxis - Severe Type I reaction with urgent airway and circulation threats.
- hypersensitivity-types-and-anaphylaxis-response - Prevention strategy for known trigger exposure.
- systemic-lupus-erythematosus - Autoimmune example connected to Type III and Type V concepts.
- rheumatoid-arthritis-autoimmune-joint-disease - Chronic autoimmune inflammatory disease linked to hypersensitivity mechanisms.
- medication-administration-safety-measures - Medication safety processes during emergency drug delivery.
Self-Check
- Which features distinguish a mild allergic reaction from evolving anaphylaxis?
- Why is intramuscular epinephrine prioritized before adjunct medications in severe reactions?
- How do Type II, III, IV, and V mechanisms differ from Type I immediate hypersensitivity?