What is the appropriate antibiotic regimen and management for a child with uncomplicated acute cellulitis (non‑purulent erythema, warmth, pain, swelling, without systemic toxicity)?

Pediatric Cellulitis Treatment

First-Line Oral Antibiotic Therapy

For uncomplicated, non-purulent pediatric cellulitis, prescribe cephalexin 25–50 mg/kg/day divided every 6 hours (or 500 mg four times daily for children ≥43 kg) for 5 days if clinical improvement occurs. 1

• Beta-lactam monotherapy achieves approximately 96% clinical success in typical pediatric cellulitis because the primary pathogens are beta-hemolytic streptococci (especially Streptococcus pyogenes) and methicillin-sensitive Staphylococcus aureus. 1, 2, 3
• Alternative oral beta-lactams include dicloxacillin 12.5–25 mg/kg/day divided every 6 hours or amoxicillin 25–50 mg/kg/day divided every 8 hours. 1
• Cefdinir 7 mg/kg every 12 hours for 10 days is FDA-approved for uncomplicated pediatric skin infections, though twice-daily dosing is required (once-daily has not been studied for skin infections). 4

Treatment Duration

Treat for exactly 5 days when warmth, tenderness, and erythema are improving and the child is afebrile; extend only if symptoms have not improved. 1, 5

• High-quality randomized controlled trial evidence shows 5-day courses are as effective as 10-day courses for uncomplicated cellulitis. 1
• Traditional 7–14-day regimens are unnecessary and promote antimicrobial resistance. 1

When to Add MRSA Coverage (and When NOT to)

Do NOT add MRSA-active antibiotics for typical non-purulent pediatric cellulitis without specific risk factors. 1, 3, 6

Add MRSA coverage ONLY when any of the following are present:

• Purulent drainage or exudate at the infection site 1, 6
• Penetrating trauma or injection drug use (rare in children but relevant in adolescents) 1
• Known MRSA colonization or prior MRSA infection 1
• Systemic inflammatory response syndrome (fever >38°C, tachycardia, tachypnea) 1
• Failure to respond to beta-lactam therapy after 48–72 hours 1

MRSA-Active Oral Regimens (when indicated)

For purulent cellulitis requiring MRSA coverage:

• Clindamycin 10–13 mg/kg/dose every 6–8 hours (maximum 40 mg/kg/day) provides single-agent coverage for both streptococci and MRSA, but use only if local clindamycin resistance <10%. 1
• Trimethoprim-sulfamethoxazole (TMP-SMX) 4–6 mg/kg/dose (based on TMP component) twice daily PLUS a beta-lactam (cephalexin or amoxicillin) ensures both MRSA and streptococcal coverage. 1
• Doxycycline 2 mg/kg twice daily (maximum 100 mg/dose) PLUS a beta-lactam is appropriate for children ≥8 years old and <45 kg; contraindicated in children <8 years due to tooth discoloration and bone growth effects. 1

Hospitalization Criteria

Admit children with cellulitis when any of the following are present:

• Age <6 months with moderate-to-severe disease 1
• Systemic inflammatory response syndrome (fever, tachycardia, hypotension, altered mental status) 1, 5
• Signs of deep or necrotizing infection (severe pain out of proportion, skin anesthesia, rapid progression, "wooden-hard" tissue, bullae, gas) 1
• Severe immunocompromise or neutropenia 1
• Failure of outpatient therapy after 24–48 hours 1

Inpatient IV Antibiotic Regimens

For hospitalized children with complicated cellulitis:

• Vancomycin 15 mg/kg IV every 6 hours is first-line therapy (Evidence grade A-II). 1
• Clindamycin 10–13 mg/kg IV every 6–8 hours is an alternative for stable children provided local MRSA clindamycin resistance <10%, with option to switch to oral when susceptible. 1, 7
• Linezolid 10 mg/kg IV every 8 hours for children <12 years (or 600 mg IV twice daily for ≥12 years) is another IV option. 1
• Treatment duration for complicated infections is 7–14 days, individualized by clinical response. 1

Practical Outpatient Management Algorithm

Step 1: Assess for purulent drainage, abscess, or MRSA risk factors

• If none present → prescribe cephalexin 25–50 mg/kg/day divided every 6 hours for 5 days 1, 8
• If purulent features or MRSA risk → prescribe clindamycin 10–13 mg/kg/dose every 6–8 hours (if local resistance <10%) OR TMP-SMX + cephalexin 1

Step 2: Reassess within 24–48 hours

• Oral regimens have reported failure rates of approximately 21% if no response is seen. 1
• If improving (reduced warmth, tenderness, erythema) → complete 5-day course 1
• If not improving → consider resistant organisms, undrained abscess, deeper infection, or hospitalization 1

Step 3: Adjunctive measures

• Elevate the affected limb above heart level several times daily to promote edema drainage. 1
• Examine interdigital toe spaces for tinea pedis and treat if present to reduce recurrence. 1

Common Pitfalls to Avoid

• Do NOT hospitalize all pediatric cellulitis cases; stable children with uncomplicated disease can be managed outpatient with close follow-up. 1, 8
• Do NOT add MRSA coverage without specific risk factors, as this overtreats approximately 96% of typical cases and drives resistance. 1, 3
• Do NOT use doxycycline or TMP-SMX as monotherapy for typical cellulitis because they lack reliable activity against beta-hemolytic streptococci. 1, 6
• Do NOT continue ineffective antibiotics beyond 48 hours if the infection is progressing; reassess for resistant organisms or deeper infection. 1
• Do NOT delay surgical consultation when signs of necrotizing infection, abscess, or systemic toxicity develop. 1

Special Considerations

• Abscesses require incision and drainage as primary treatment; antibiotics play only a subsidiary role and may be unnecessary for simple abscesses without surrounding cellulitis. 1, 6
• Cefazolin 50 mg/kg/day IV divided every 8 hours (or cefazolin with probenecid for twice-daily dosing) is effective for children requiring IV therapy, with lower failure rates than cefazolin alone. 8, 7
• Oral antibiotics require fewer visits and less time in the emergency department compared with IV treatment (1.4 vs. 3.4 visits; 164 vs. 521 minutes). 8