Stinging insect hypersensitivity

Question 1

How many children have systemic allergic reactions to insect stings?

Answer 1

0.4-0.8% of children

Question 2

What stinging insects cause systemic allergic reactions?

Answer 2

hornets, wasps, yellow jackets, honeybees

• yellow jacket cause most frequent insect reactions

Question 3

What are 2 types of IgE mediated reactions to insect stings?

Answer 3

1. large local reaction (10 cm swelling or more in diametre)
   - increases in size for 1-2 days, resolves over 3-10 days
2. systemic reaction to insect sting

Question 4

How to differentiate bw cellulitis and large local reaction to insect sting?

Answer 4

• only consider dx of cellulitis if there are systemic symptoms (fever)

Question 5

How do you manage a large local reaction to insect sting?

Answer 5

• Acute Management
  
  • low risk for systemic reaction, require supportive therapy only
    
    • oral non-sedating antihistamines
    • cold compresses
    • oral analgesics
    • or brief course of oral corticosteroid
• Long-term management
  
  • no IM epi
  • review avoidance with family

Question 6

What are symptoms of systemic reaction to insect sting?

Answer 6

• symptoms: cutaneous (urticaria, angioedema), GI (vomiting, diarrhea), respiratory (wheeze, cough), cardiovascular (hypotension, syncope)
• occur within 5-30 minutes after insect sting
• can occur without history of reaction to stings in past

Question 7

What is acute management of systemic reaction to insect sting?

Answer 7

• epi 0.01 mg/kg IM - max 0.3 mg in prepubertal child, 0.5 mg in adolescent
• observe 4-6 hours
  
  • may need longer for kids at risk of biphasic reaction:
    
    • delayed presentation to ED
    • needed more than one dose epi
    • received beta-agonist
    • presented with wide pulse pressure

Question 8

What is long term management of systemic reaction to insect sting?

Answer 8

carry epi auto-injector (EXCEPT for those who experience isolated systemic cutaneous reactions)

• Refer allergist (unless isolated systemic cutaneous reaction when only system involved is the skin)

Question 9

Who can get venom immunotherapy?

Answer 9

positive skin test & history of systemic reaction
EXCEPT if the reaction was skin reaction alone

if history of severe reaction and skin testing negative, serum-specific IgE and repeat skin testing is ordered; if both are negative, the chance of a future systemic reaction to a stinging insect is minimal

Question 10

How much does VIT reduce risk for future systemic reactions?

Answer 10

30 to 5%

Question 11

How is VIT administered?

Answer 11

• administered over 3-5 yrs
• increasing dose build-up phase: weekly SC injections
• maintenance phase: once q4 weeks over 1-2 years
• Then q8-12 weeks

Question 12

If someone is anphylactic to yellow jacket and hornet venom, what should they get VIT for?

Answer 12

• cross reactivity b/w yellow jacket & hornet venom - therefore VIT for just one provides coverage for all 3
  
  • less cross-reactivity for wasp and rare for honeybee

Question 13

In maintenance phase of VIT, who needs to carry an EpiPen?

Answer 13

• hx near-fatal reaction or systemic reactoion during treatment in cases with severe honeybee allergy
• elevated baseline serum tryptase level
• underlying medical condition
• or for people likely to have exposure

Question 14

What bloodwork do you do for people who have hx of severe anaphylaxis to insect sting??

Answer 14

baseline serum tryptase blood test

Why?

• implications for prognosis: higher risk for systemic reactions to stinging insects in future and failure to respond to VIT
• > 20 ng/mL may indicate comorbid condition of systemic mastocytosis