II. Epidemiology
- Responsible for at least 50 U.S. fatalities yearly
-
Incidence of systemic reaction to Stinging Insect
- Adults: 3%
- Children: 1%
III. Background
IV. Signs
- See Allergic Reaction
- Systemic reactions (IgE mediated)
- Anaphylaxis
- Large local swelling at bite (8-10 inch diameter)
- Develops over 2 days
- Resolves within 7 days
V. Differential Diagnosis
- See Insect Bite
VI. Diagnosis: Hymenoptera venom tests
-
Intradermal Testing
- Requires each venom type be tested (see background)
- Venom dose varies from 0.001 to 1.0 mcg/ml
- Do not test without history of reaction
- Test Sensitivity: 65-80%
- False Negatives: Too early after bite (<6 weeks)
-
RAST testing
- May be useful to clarify Skin Testing
- Sensitivity level does not correlate with reaction
VII. Management
- See Anaphylaxis
VIII. Prevention
- See Allergic Reaction
- See Insect Bite
- See Prevention of Vector-borne Infection
-
Immunotherapy with venoms
- Protects in 98% of cases against severe reaction
- Mixed vespid venom higher efficacy than individual
- Local reactions occur in 50% of patients
- Most often occurs at starting doses <50 mcg
- Titrate up to maintenance dosing
- Individual venom: 100 mcg
- Mixed vespid venom: 300 mcg
- Continue maintenance for at least one year
- Once on full dose, dose monthly
- May ultimately be spread to every 6-8 weeks
IX. Monitoring during Desensitization
- Consider skin retesting every 2-5 years
-
Venom skin tests after Desensitization
- Negative at 5 years: <20% of cases
- Negative at 7-10 years: 50-60%
X. Prognosis: Future risk of systemic reaction
- Skin-test confirmed recurrence risk declines with time
- Initially: 50%
- Year 3-5: 35%
- Year 10: 25%
- Risk decreases with duration of Desensitization
- Reactions uncommon on Desensitization maintenance
- Reactions after Desensitization are usually more mild
- Desensitization stopped <2 years: High reaction risk
- Desensitization stopped 5 years: 10% reaction risk
XI. Resources
- AAAAI Stinging Insect Allergy Prevention