What is the recommended treatment for insect bite reactions?

Treatment of Insect Bite Reactions

For local insect bite reactions, apply cold compresses and administer oral antihistamines (cetirizine preferred over diphenhydramine due to minimal sedation), while systemic reactions require immediate intramuscular epinephrine (0.01 mg/kg up to 0.3 mg in children, 0.3-0.5 mg in adults) injected in the anterolateral thigh. 1, 2, 3

Immediate Management Based on Reaction Type

Local Reactions (Most Common)

Local reactions present with redness, swelling, itching, and pain at the bite site, typically resolving within hours to days. 1

Treatment approach:

• Remove stinger immediately by plucking or scraping if present 3
• Wash area with soap and water 3
• Apply ice or cold compresses to reduce pain and swelling 3, 4
• Administer oral antihistamines (cetirizine recommended by the American Academy of Allergy, Asthma, and Immunology over diphenhydramine due to minimal sedation) 2
• Apply topical corticosteroids (hydrocortisone) to reduce itching 3, 5

Large Local Reactions

These are IgE-mediated reactions causing swelling extending beyond the sting site (>10 cm diameter), peaking at 24-48 hours and lasting up to a week or more, affecting 5-15% of patients. 1, 4

Treatment approach:

• Cold compresses for pain and swelling reduction 4
• Oral antihistamines for itching and pain 4
• Oral corticosteroids may be considered for severe large local reactions 4
• Critical pitfall: Do NOT mistake allergic swelling and lymphangitis for bacterial cellulitis—antibiotics are not indicated unless there is purulent drainage, fever, or progressive worsening beyond 48-72 hours despite anti-inflammatory treatment 4

Systemic Reactions (Life-Threatening)

Systemic reactions include cutaneous manifestations (widespread hives, angioedema), respiratory symptoms (bronchospasm, laryngospasm), and cardiovascular collapse, occurring in 0.4-0.8% of children and up to 3% of adults. 1, 2, 6

Immediate treatment protocol:

• Administer epinephrine 0.01 mg/kg (up to 0.3 mg in children, 0.3-0.5 mg in adults) intramuscularly in the anterolateral thigh immediately—this achieves faster and higher plasma concentrations than subcutaneous or arm injections 1, 3, 6
• Delayed epinephrine use is associated with fatal outcomes 1, 3
• Be prepared to repeat epinephrine dose in 10-20 minutes if symptoms persist or worsen 3
• Place patient in recumbent position with legs elevated if hypotension develops 3
• Activate emergency response system immediately 3
• Consider oral corticosteroids to prevent biphasic reactions (no immediate effect) 3

Post-Acute Management and Prevention

For Patients with Systemic Reactions

All patients who experience systemic reactions must:

• Receive prescription for epinephrine autoinjector (consider prescribing more than one device as some patients require multiple injections) 1
• Carry epinephrine at all times 1
• Receive education on autoinjector use and indications 1, 3
• Be referred to allergist-immunologist for venom-specific IgE testing and consideration of venom immunotherapy (VIT) 1, 3
• Consider medical identification bracelet or necklace 1

Important exception: Children 16 years and younger who experience only cutaneous systemic reactions (isolated hives/angioedema without respiratory or cardiovascular symptoms) generally do not require venom immunotherapy. 1, 2

Venom Immunotherapy Considerations

VIT reduces the risk of subsequent systemic reactions to less than 5% and is highly effective. 1, 7

VIT is indicated for:

• Adults with any systemic reaction beyond isolated cutaneous manifestations 1
• Patients with unavoidable frequent exposure and large local reactions 1
• Patients with severe anaphylaxis history (may require extended or indefinite duration) 1

VIT duration: Typically 3-5 years, though patients with history of severe anaphylaxis with shock or loss of consciousness may benefit from extended or indefinite therapy. 1

Avoidance Education

Teach all at-risk patients to:

• Have known nests removed by professionals 1, 3
• Avoid brightly colored clothing, flowery prints, and strongly scented products 1, 3
• Wear long pants, long-sleeved shirts, socks, shoes, and gloves when working outdoors 1
• Avoid walking barefoot or in open shoes (sandals) 1, 3
• Be cautious near bushes, eaves, attics, garbage containers, and picnic areas 1, 3
• Avoid eating or drinking outdoors when possible 1, 3
• Keep insecticides for stinging insects readily available 1

Special Considerations

Coexisting conditions: There is no contraindication to epinephrine use in life-threatening anaphylaxis, even in patients with hypertension, cardiac arrhythmias, or those taking β-blockers—these patients require special attention but must still receive epinephrine. 1

Eye stings: Any sting to the eye itself (not just eyelid) requires immediate medical evaluation due to risk of permanent vision loss. 3

Multiple stings: Typically >100 stings can cause toxic reactions due to massive envenomation, requiring emergency evaluation. 3