What is the recommended treatment for a patient with a bug bite, considering potential allergic reactions and transmission of diseases like Lyme disease or Zika virus?

Bug Bite Treatment

Immediate Assessment and Emergency Management

For any systemic symptoms (urticaria, angioedema, respiratory distress, hypotension, gastrointestinal symptoms), administer epinephrine 0.3-0.5 mg intramuscularly in the anterolateral thigh immediately—antihistamines and corticosteroids are NOT substitutes for epinephrine in anaphylaxis. 1, 2, 3

• Intramuscular injection in the anterolateral thigh achieves more rapid and higher plasma concentrations than subcutaneous or arm injection 1
• Repeat dosing may be required for persistent or recurrent symptoms 1, 2
• Delayed epinephrine use is associated with fatal outcomes 4
• Transport to emergency department for observation and additional treatment after epinephrine administration 2

Standard Local Reaction Treatment

Most insect bites require only symptomatic care—the swelling is caused by allergic mediator release, not infection, so antibiotics are not indicated unless clear signs of secondary bacterial infection develop. 2, 4

First-line symptomatic measures:

• Apply cold compresses to reduce local pain and swelling 2
• Oral antihistamines for itching, pain, and inflammation 2, 4
• Oral analgesics for pain management 2
• Elevate the affected limb if swelling is significant 2

Large local reactions (extensive swelling):

• Consider oral corticosteroids for severe cases, though definitive controlled trial evidence is lacking 2, 4
• These reactions typically increase in size for 24-48 hours and take 5-10 days to resolve 2
• Large local reactions represent IgE-mediated allergic inflammation, not infection 2

When to Use Antibiotics

Prescribe antibiotics ONLY if clear signs of secondary bacterial infection are present: 2, 4

• Progressive redness beyond the initial reaction area
• Increasing pain after initial improvement
• Purulent discharge
• Fever
• Warmth and tenderness suggesting cellulitis

Common pitfall: Do not prescribe antibiotics for local swelling alone—this contributes to antibiotic resistance without providing benefit 4

Special Bite Types

Fire Ant Stings:

• Characteristically produce a sterile pseudopustule within 24 hours, which is pathognomonic and NOT infected 2, 4
• Leave the vesicle intact and keep clean to prevent secondary infection 2

Tick Bites (Lyme Disease Prevention):

For high-risk tick bites (ALL three criteria must be met: Ixodes species, endemic area, attached ≥36 hours), give a single dose of doxycycline 200 mg for adults or 4.4 mg/kg (max 200 mg) for children ≥8 years within 72 hours of tick removal. 5

• Doxycycline is contraindicated in pregnant women and children <8 years 5, 6
• Amoxicillin is NOT recommended as prophylaxis due to lack of data on effective short-course regimens 5
• Testing the tick for B. burgdorferi is not recommended 5
• Do not perform diagnostic testing on asymptomatic patients after tick bites 5
• Instruct patients to monitor for erythema migrans or flu-like symptoms for 30 days 5

Referral to Allergist-Immunologist

Refer patients who have experienced ANY systemic reaction to an insect sting for evaluation and consideration of venom immunotherapy (VIT). 1, 4

Indications for referral: 1

• History of systemic allergic reaction to insect sting
• Need for education about risk, emergency treatment, and avoidance
• Coexisting conditions or medications that complicate anaphylaxis treatment (β-blockers, cardiac disease)
• Large local reactions with vascular compromise 4

Venom immunotherapy considerations:

• VIT reduces risk of subsequent systemic reaction to <5% 1, 4
• Generally NOT necessary in children ≤16 years with isolated cutaneous systemic reactions 1
• Recommended for adults with systemic reactions and positive venom-specific IgE testing 1, 4
• Should be continued for 3-5 years minimum 1, 4
• Skin testing may be falsely negative within 6 weeks of reaction and require retesting 1, 4

Patient Education and Prevention

All patients with history of systemic reactions should: 1

• Carry autoinjectable epinephrine at all times
• Be trained on proper epinephrine administration technique
• Understand when to use epinephrine (any systemic symptoms)
• Consider medical identification bracelet or necklace
• Learn insect avoidance measures

Avoidance measures: 1

• Have nests near home removed by trained professionals
• Use EPA-registered insect repellents 5
• Wear protective clothing in high-risk areas
• Perform regular tick checks after outdoor activities 5

Critical pitfall: Approximately 30-60% of patients with history of systemic reaction and positive IgE testing will experience another systemic reaction if re-stung without VIT 1