What is the treatment for an insect bite hypersensitivity reaction?

Treatment for Insect Bite Hypersensitivity Reactions

Immediate administration of intramuscular epinephrine is the first-line treatment for systemic allergic reactions to insect stings, with a dose of 0.3-0.5 mg in adults and 0.01 mg/kg up to 0.3 mg in children. 1, 2

Classification and Management of Reactions

Local Reactions

• Clean wound thoroughly with soap and water
• Remove stinger immediately (if present) - speed is more important than method 1
• Apply cold compresses or ice packs (with a thin barrier) to reduce pain and swelling
• Use oral antihistamines for itching
• Consider acetaminophen or NSAIDs for pain relief 1

Large Local Reactions

• Manage similarly to local reactions
• Venom immunotherapy (VIT) is generally not necessary as risk of systemic reaction is low 3
• However, VIT may be considered for patients with frequent, unavoidable large local reactions as it can reduce their size and duration 3

Systemic Reactions (Anaphylaxis)

1. Immediate Management:

   • Administer epinephrine intramuscularly as first-line treatment 1, 2
   • H1 antihistamines, H2 antihistamines, and corticosteroids may help with symptoms but should never delay epinephrine administration 1
   • Monitor patient for at least 4-6 hours after treatment for delayed or biphasic reactions 1

2. Follow-up Management:

   • Prescribe autoinjectable epinephrine for patients with history of systemic reactions 3, 1
   • Consider prescribing multiple epinephrine injectors as some patients may require more than one dose 3
   • Refer to allergist-immunologist for evaluation and consideration of venom immunotherapy 1

Venom Immunotherapy (VIT)

Indications

• Recommended for patients with:
  • History of systemic allergic reactions to insect stings
  • Positive skin or in vitro test for specific IgE antibodies to venom allergens 3, 1

Effectiveness and Duration

• Reduces risk of subsequent systemic reactions to less than 5% 3, 1
• Typically continued for 3-5 years 1
• Extended duration (possibly indefinitely) may be considered for high-risk patients 3

Special Considerations

• VIT is generally not necessary in children 16 years and younger who have experienced only isolated cutaneous systemic reactions 3
• For adults with only cutaneous manifestations, VIT is controversial but usually recommended 3
• Patients with severe insect sting reactions should be evaluated for mast cell disorders (including baseline serum tryptase measurement) 3

Prevention Strategies

• Have known insect nests removed by professionals
• Avoid wearing bright colors or flowery prints
• Wear protective clothing (long pants, long sleeves, closed shoes) 1
• Educate patients and caregivers on proper use of epinephrine autoinjectors 3, 1

Important Caveats

• Even patients with coexisting conditions (hypertension, cardiac arrhythmias) or on medications like β-blockers should receive epinephrine for anaphylaxis 3
• Approximately 30-60% of patients with history of systemic reactions and positive venom-specific IgE will experience a systemic reaction when re-stung if not treated with VIT 3
• Rarely (<1% of patients), individuals can have anaphylactic reactions to subsequent stings despite negative skin and in vitro test results 3
• Corticosteroids like prednisone may be used for managing allergic manifestations but should not replace epinephrine for anaphylaxis 4

This approach prioritizes rapid intervention for life-threatening reactions while providing appropriate management for milder manifestations of insect bite hypersensitivity.