II. Epidemiology

  1. Responsible for at least 50 U.S. fatalities yearly
  2. Incidence of systemic reaction to Stinging Insect
    1. Adults: 3%
    2. Children: 1%

III. Background

  1. Usually only Insects of Hymenoptera cause Anaphylaxis
  2. Distinct InsectVenoms (allergy specific to types)
    1. Honeybee and Bumblebee Venom
    2. Yellow Jacket and Hornet Venom
    3. Polistes Wasp
    4. Fire ants

IV. Signs

  1. See Allergic Reaction
  2. Systemic reactions (IgE mediated)
    1. Anaphylaxis
    2. Large local swelling at bite (8-10 inch diameter)
      1. Develops over 2 days
      2. Resolves within 7 days

V. Differential Diagnosis

VI. Diagnosis: Hymenoptera venom tests

  1. Intradermal testing
    1. Requires each venom type be tested (see background)
    2. Venom dose varies from 0.001 to 1.0 mcg/ml
    3. Do not test without history of reaction
    4. Test Sensitivity: 65-80%
      1. False negatives: Too early after bite (<6 weeks)
  2. RAST testing
    1. May be useful to clarify Skin Testing
    2. Sensitivity level does not correlate with reaction

VII. Management

VIII. Prevention

  1. See Allergic Reaction
  2. See Insect Bite
  3. See Prevention of Vector-borne Infection
  4. Immunotherapy with venoms
    1. Protects in 98% of cases against severe reaction
    2. Mixed vespid venom higher efficacy than individual
    3. Local reactions occur in 50% of patients
      1. Most often occurs at starting doses <50 mcg
    4. Titrate up to maintenance dosing
      1. Individual venom: 100 mcg
      2. Mixed vespid venom: 300 mcg
    5. Continue maintenance for at least one year
      1. Once on full dose, dose monthly
      2. May ultimately be spread to every 6-8 weeks

IX. Monitoring during desensitization

  1. Consider skin retesting every 2-5 years
  2. Venom skin tests after desensitization
    1. Negative at 5 years: <20% of cases
    2. Negative at 7-10 years: 50-60%

X. Prognosis: Future risk of systemic reaction

  1. Skin-test confirmed recurrence risk declines with time
    1. Initially: 50%
    2. Year 3-5: 35%
    3. Year 10: 25%
  2. Risk decreases with duration of desensitization
    1. Reactions uncommon on desensitization maintenance
    2. Reactions after desensitization are usually more mild
    3. Desensitization stopped <2 years: High reaction risk
    4. Desensitization stopped 5 years: 10% reaction risk

XI. Resources

  1. AAAAI Stinging Insect Allergy Prevention
    1. http://www.aaaai.org/patients/publicedmat/tips

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