NCLEX Review Guide: Hypersensitivity and Allergy

Type I - Immediate Hypersensitivity (IgE-mediated)

• Anaphylaxis is the most severe form, occurring within minutes of exposure to allergens like medications, foods, or insect stings.
• Symptoms progress rapidly from urticaria and pruritus to respiratory distress, cardiovascular collapse, and potential death without immediate intervention.

Type II - Cytotoxic (Antibody-mediated)

• Involves complement activation leading to cell destruction, commonly seen in transfusion reactions and hemolytic anemia.
• Occurs when antibodies bind to antigens on cell surfaces, marking them for destruction by immune cells.

Type III - Immune Complex

• Results from antigen-antibody complexes depositing in tissues, causing inflammation in joints, kidneys, and blood vessels.
• Examples include systemic lupus erythematosus and rheumatoid arthritis with characteristic joint pain and organ involvement.

Type IV - Delayed Hypersensitivity (T-cell mediated)

• Reaction occurs 24-72 hours after exposure, involving T-lymphocytes rather than antibodies.
• Classic example is contact dermatitis from poison ivy or tuberculin skin test reactions.

Emergency Interventions

1. Epinephrine 1:1000 IM immediately - first-line treatment for anaphylaxis
2. Establish airway and administer high-flow oxygen
3. IV access with normal saline for fluid resuscitation
4. Position patient supine with legs elevated (Trendelenburg)
5. Continuous cardiac monitoring and vital signs

Secondary Medications

• Diphenhydramine (Benadryl) 25-50mg IV/IM for histamine blockade and symptom relief.
• Corticosteroids like methylprednisolone to prevent biphasic reactions that can occur 4-12 hours later.
• Bronchodilators (albuterol) if significant bronchospasm is present.

High-Risk Allergens

• Medications: Penicillin, NSAIDs, contrast dyes, and chemotherapy agents are frequent triggers.
• Foods: The "Big 8" include milk, eggs, peanuts, tree nuts, soy, wheat, fish, and shellfish.
• Environmental: Latex, insect stings, and airborne allergens like pollen and dust mites.

Assessment Findings

• Respiratory symptoms: Wheezing, stridor, dyspnea, and sensation of throat tightness indicate airway involvement.
• Cardiovascular symptoms: Tachycardia, hypotension, and weak pulse suggest vascular compromise and shock.
• Skin manifestations: Urticaria, angioedema, flushing, and pruritus are common early signs.

Allergy Management

• Patients with known severe allergies should carry EpiPen auto-injectors and understand proper administration technique.
• Medical alert bracelets or necklaces should clearly identify specific allergens to inform healthcare providers during emergencies.
• Teach patients to read food labels carefully and understand cross-contamination risks in food preparation.

Desensitization Therapy

• Immunotherapy involves gradual exposure to increasing amounts of allergen to build tolerance over time.
• Most effective for environmental allergens like pollen, dust mites, and insect venom rather than food allergies.