What is the appropriate treatment for an allergic reaction to bug bites?

Treatment of Allergic Reactions to Bug Bites

For allergic reactions to bug bites, first-line treatment includes cold compresses, oral antihistamines, elevation of the affected area, and topical corticosteroids. For severe local reactions, a short course of oral corticosteroids may be needed. Systemic reactions require immediate epinephrine administration. 1

Classification and Management of Reactions

Localized Reactions

1. First-line treatments:

   • Apply cold compresses to reduce swelling and pain 1
   • Use oral antihistamines for itch relief 1
   • Elevate the affected area 1
   • Apply topical corticosteroids for delayed hypersensitivity reactions 1
   • Topical lidocaine may help relieve local pain if skin is intact 1

2. For severe local reactions:

   • Short course of oral corticosteroids may be necessary 1
   • Monitor the bite site for 48-72 hours for signs of infection 1

Systemic Reactions (Anaphylaxis)

Systemic allergic reactions occur in 0.4-0.8% of children and up to 3% of adults, usually within 10 minutes of the sting 1.

1. Emergency treatment:

   • Immediate administration of epinephrine is critical and life-saving 1, 2, 3
     • Adult dosage: 0.3-0.5 mg intramuscularly into anterolateral thigh
     • Children ≥30 kg: 0.3-0.5 mL intramuscularly into anterolateral thigh
   • Transport to emergency department for monitoring and supportive care 1

2. Adjunct medications (only after epinephrine administration):

   • Antihistamines (H1 and H2 antagonists) 3
   • Corticosteroids 3
   • Beta2 agonists for bronchospasm 3

Important Clinical Considerations

Signs of Infection

Monitor for signs of infection requiring antibiotic treatment 1:

• Increasing redness, warmth, swelling
• Purulent discharge
• Fever
• Lymphangitis

If infection develops, first-line antibiotics include:

• Amoxicillin-clavulanate 875/125 mg twice daily
• Cephalexin 250 mg four times daily
• Clindamycin 300-400 mg three times daily (for penicillin-allergic patients) 1

Common Pitfalls to Avoid

1. Delayed epinephrine administration in anaphylaxis - this has been associated with fatal reactions 1, 4
2. Relying solely on antihistamines for anaphylaxis - antihistamines do not relieve all symptoms of anaphylaxis and act more slowly than epinephrine (1-3 hours vs. <10 minutes) 4
3. Closing infected wounds - this can lead to further complications 1
4. Failure to refer patients with systemic reactions to an allergist 1

Prevention Strategies

1. Physical protection:

   • Wear long pants, long-sleeved shirts, socks, and closed shoes outdoors 1
   • Avoid walking barefoot or with open shoes 1

2. Environmental measures:

   • Remove known nests near home (using trained professionals) 1
   • Avoid areas with high uncut grass, weeds, and low brush 1
   • Be cautious near bushes, eaves, and attics 1

3. For high-risk individuals:

   • Patients with history of systemic reactions should carry injectable epinephrine 1, 5
   • Referral to an allergist for evaluation for venom immunotherapy 1

Follow-up Care

• Follow-up within 24 hours by phone or office visit for significant reactions 1
• Patients who experienced systemic reactions should:
  • Be referred to an allergist 1
  • Receive education about risk of future reactions 1
  • Learn about emergency treatment options 1
  • Be evaluated for venom immunotherapy 1
  • Be monitored for 4-12 hours for potential biphasic reactions 3