What is the first‑line therapy for impetigo, including topical and oral options based on the extent of skin involvement?

Impetigo Treatment

First-Line Therapy Based on Disease Extent

For limited impetigo (few lesions, <100 cm²), topical mupirocin 2% ointment applied twice to three times daily for 5 days is the first-line treatment and is superior to oral antibiotics. 1, 2 Retapamulin 1% ointment twice daily for 5 days is an effective alternative for patients ≥9 months of age. 1, 2

For extensive impetigo (numerous lesions, multiple body sites, or when topical therapy is impractical), oral antibiotics are required for 7 days. 1, 2

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Oral Antibiotic Selection Algorithm

When Methicillin-Susceptible S. aureus (MSSA) Is Presumed

Cephalexin is the preferred first-line oral agent:

• Adults: 250–500 mg four times daily for 7 days 1
• Children: 25–50 mg/kg/day divided into 3–4 doses for 7 days 1

Dicloxacillin is an equally effective alternative:

• Adults: 250 mg four times daily for 7 days 1
• Children: 25–50 mg/kg/day divided into 4 doses for 7 days 1

Amoxicillin-clavulanate (co-amoxiclav) is an acceptable alternative when cephalexin or dicloxacillin are unsuitable, dosed for 7 days. 1

When MRSA Is Suspected or Confirmed

Switch to an MRSA-active agent immediately if:

• Purulent drainage is present 1
• Prior treatment with beta-lactams has failed 1
• Local community-acquired MRSA prevalence exceeds 10% 1

MRSA-active oral options (all for 7 days):

• Clindamycin: 300–450 mg three to four times daily (adults); 20–30 mg/kg/day divided into 3 doses (children) 1, 2
• Trimethoprim-sulfamethoxazole: 1–2 double-strength tablets twice daily (adults); 8–12 mg/kg/day (trimethoprim component) divided twice daily (children) 1, 2
• Doxycycline (only for patients >8 years): 100 mg twice daily (adults); 2–4 mg/kg/day divided twice daily (children >8 years) 1

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Critical Pitfalls to Avoid

• Do not use cephalexin, dicloxacillin, or any beta-lactam when MRSA is documented or strongly suspected—they lack MRSA activity. 1
• Do not prescribe oral antibiotics for limited disease when topical mupirocin is appropriate and more effective. 1
• Do not shorten oral therapy to less than 7 days—shorter courses increase failure and recurrence risk. 1
• Do not use penicillin alone; it is seldom effective because it lacks adequate S. aureus coverage. 1, 3
• Do not use amoxicillin alone—it does not cover S. aureus adequately. 1
• Do not use erythromycin or azithromycin routinely due to rising resistance rates. 1, 3
• Do not use tetracyclines (doxycycline) in children <8 years due to permanent dental staining risk. 1

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Special Populations

Penicillin Allergy

• Cephalexin may be used in non-immediate hypersensitivity (cross-reactivity <5%). 1
• For immediate hypersensitivity (anaphylaxis, angioedema, urticaria), use clindamycin instead. 1

Pregnancy

• Cephalexin is considered safe during pregnancy. 1

Breastfeeding

• Cephalexin, dicloxacillin, trimethoprim-sulfamethoxazole, and doxycycline are safe for short-term use while breastfeeding. 1
• In neonates ≤28 days, jaundiced infants, or those with G6PD deficiency, avoid trimethoprim-sulfamethoxazole and use clindamycin instead. 1

Immunocompromised or Diabetic Patients

• Consider a lower threshold for systemic antibiotics and hospital admission if extensive disease or systemic signs are present. 1

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Infection Control Measures

Concurrent hygiene interventions are essential to prevent spread:

• Keep draining lesions covered with clean, dry dressings 1, 2
• Perform regular hand hygiene with soap and water or alcohol-based hand rubs 1, 2
• Do not share personal items that contact skin (razors, towels, linens, clothing) 1, 2
• Clean high-touch surfaces (counters, doorknobs, bathtubs) that may contact bare skin 1
• Wash all clothing, towels, and bedding in hot water daily during the first few days of therapy 2
• Trim fingernails short to reduce scratching and transmission 2

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Activity Restrictions

• Keep children home from school, daycare, and organized sports until at least 24 hours after initiating antibiotic treatment. 2
• Avoid close-contact sports and swimming pools until lesions are fully healed and no longer draining. 2

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When to Obtain Cultures

Obtain cultures of vesicle fluid, pus, or erosions if:

• Treatment failure occurs 4
• MRSA is suspected 4
• Recurrent infections are present 4

Adjust antimicrobial therapy based on susceptibility results. 4

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Follow-Up and Warning Signs

• Re-evaluate if no improvement after 48–72 hours of therapy. 4
• Seek prompt evaluation if fever develops or worsens during treatment, or if redness expands beyond original lesions. 2
• Examine siblings and close contacts for new lesions, as impetigo spreads easily within families. 2

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Adjunctive Local Wound Care

• Gently wash affected areas with soap and water before applying topical antibiotics. 2
• Soak lesions with warm, soapy water to soften crusts before applying medication, enhancing antibiotic penetration. 2
• Apply plain petrolatum ointment and bandages over open erosions after bullae have deroofed. 1