What is the treatment for a 25-year-old female with a swollen and infected insect bite, assuming no known allergies or contraindications?

Treatment of Swollen and Infected Insect Bite

For a 25-year-old female with a swollen insect bite, start with symptomatic care using cold compresses, oral antihistamines, and elevation—do NOT prescribe antibiotics unless there are clear signs of secondary bacterial infection such as purulent discharge, progressive redness, increasing pain, or fever. 1

Understanding the Swelling

The swelling you're seeing is almost certainly allergic inflammation from mediator release, not infection. 1, 2 This is a critical distinction that prevents antibiotic overuse:

• Most insect bite swelling represents an IgE-mediated allergic reaction that peaks at 24-48 hours and resolves over 5-10 days 1
• The inflammation is caused by histamine and other mediators, not bacteria 1, 2
• Recent UK data shows antibiotics are prescribed for nearly three-quarters of insect bites, representing significant overuse 3

Initial Management Algorithm

First-Line Treatment (for all patients)

• Apply cold compresses to reduce pain and swelling 1, 4
• Prescribe oral antihistamines to reduce itching, pain, and inflammation 1, 4, 2
• Elevate the affected limb if swelling is significant 1, 4
• Oral analgesics for pain control as needed 1, 2

For Large Local Reactions

• Consider oral corticosteroids if there is extensive swelling, though controlled trial evidence is limited 1, 4, 2
• Continue antihistamines and cold compresses 2
• Reassure the patient that resolution typically takes 5-10 days 1

When to Actually Prescribe Antibiotics

Only prescribe antibiotics if you document these specific signs of secondary bacterial infection: 1, 2

• Progressive redness (expanding beyond the initial reaction)
• Increasing pain (worsening rather than improving)
• Purulent discharge
• Fever
• Warmth and tenderness suggesting cellulitis

If true infection is present, cephalexin or flucloxacillin are appropriate first-line agents. 5, 3

Critical Pitfalls to Avoid

Do not mistake allergic inflammation for infection. 1, 2 The most common error is prescribing antibiotics for normal insect bite reactions:

• Fire ant stings characteristically produce a sterile pseudopustule within 24 hours—this is pathognomonic and NOT infected 1
• Leave these vesicles intact and keep them clean to prevent actual secondary infection 1
• Secondary bacterial infection is actually uncommon following insect bites 2

Red Flags Requiring Immediate Action

Monitor for systemic allergic reactions and be prepared to administer epinephrine immediately if any develop: 1, 4

• Urticaria beyond the bite site
• Angioedema
• Respiratory distress (wheezing, throat tightness)
• Hypotension
• Gastrointestinal symptoms (nausea, vomiting, cramping)

Dose: 0.3-0.5 mg intramuscularly in the anterolateral thigh, with repeat dosing as needed 4

Special Considerations

• Vascular compromise (increasing pain, numbness, coolness, color changes) requires immediate emergency evaluation 4
• Topical hydrocortisone can be used for minor itching and inflammation 6
• Consider allergist referral if the patient experiences large local reactions with vascular compromise or has any history of systemic reactions 1, 4

Patient Education

Advise the patient that:

• Swelling may continue to increase for 24-48 hours before improving 1
• Complete resolution typically takes 5-10 days 1
• They should return only if signs of true infection develop (purulent discharge, fever, progressive worsening) 1, 2
• Antihistamines can be taken before consulting for future bites 3