What is the recommended treatment for lip cellulitis?

Treatment of Lip Cellulitis

For lip cellulitis, use oral cephalexin 500 mg every 6 hours or dicloxacillin 250-500 mg every 6 hours for 5 days if clinical improvement occurs, extending only if symptoms have not improved within this timeframe. 1, 2

First-Line Antibiotic Selection

• Beta-lactam monotherapy is the standard of care for typical lip cellulitis, with a 96% success rate, as MRSA is an uncommon cause even in high-prevalence settings. 1, 2

• Cephalexin 500 mg orally every 6 hours provides effective coverage against streptococci (the primary pathogen) and methicillin-sensitive S. aureus. 1, 2

• Dicloxacillin 250-500 mg orally every 6 hours is equally effective as first-line therapy for uncomplicated cellulitis. 1, 3

• Amoxicillin-clavulanate 875/125 mg twice daily is an appropriate alternative, particularly if there is concern for beta-lactamase-producing organisms or recent amoxicillin use. 1, 2

Treatment Duration

• Treat for exactly 5 days if clinical improvement is evident; extend treatment only if the infection has not improved within this timeframe. 1, 2

• Five-day courses are as effective as 10-day courses for uncomplicated cellulitis based on high-quality randomized controlled trial evidence. 1, 2

When to Add MRSA Coverage

• Do NOT routinely add MRSA coverage for typical lip cellulitis without specific risk factors. 1, 2

• Add MRSA-active antibiotics ONLY when specific risk factors are present: 1, 2

  • Penetrating trauma or injection drug use
  • Purulent drainage or exudate visible
  • Evidence of MRSA infection elsewhere or known nasal MRSA colonization
  • Systemic inflammatory response syndrome (SIRS): fever, tachycardia, hypotension, altered mental status

• If MRSA coverage is needed, use clindamycin 300-450 mg orally every 6 hours as monotherapy (covers both streptococci and MRSA). 1, 4

• Alternative MRSA regimens include trimethoprim-sulfamethoxazole (1-2 DS tablets twice daily) PLUS a beta-lactam (cephalexin or amoxicillin), or doxycycline 100 mg twice daily PLUS a beta-lactam. 1, 2

Penicillin Allergy Considerations

• For patients with penicillin allergy, clindamycin 300-450 mg orally every 6 hours is the preferred option, as 99.5% of S. pyogenes strains remain susceptible. 1, 4

• Clindamycin should be taken with at least 4 fluid ounces (120 mL) of water and not in the supine position or immediately before bed to avoid esophageal irritation. 4

Hospitalization Criteria

• Admit patients with any of the following: 1, 2
  • SIRS criteria (fever >38°C, heart rate >90, respiratory rate >24, WBC >12,000 or <4,000)
  • Hemodynamic instability or hypotension
  • Altered mental status or confusion
  • Severe immunocompromise or neutropenia
  • Concern for deeper or necrotizing infection (severe pain out of proportion to exam, skin anesthesia, rapid progression, bullous changes)
  • Failure of outpatient treatment after 24-48 hours

Severe Infections Requiring IV Therapy

• For hospitalized patients with severe lip cellulitis and systemic toxicity, use vancomycin 15-20 mg/kg IV every 8-12 hours PLUS piperacillin-tazobactam 3.375-4.5 g IV every 6 hours. 1, 2

• Alternative IV regimens for MRSA coverage include linezolid 600 mg IV twice daily, daptomycin 4 mg/kg IV once daily, or clindamycin 600 mg IV every 8 hours (if local resistance <10%). 1, 2

Adjunctive Measures

• Treat predisposing conditions such as angular cheilitis, herpes labialis, eczema, or trauma to reduce recurrence risk. 1, 2

• Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic adults to potentially hasten resolution, though evidence is limited. 1, 2

• Avoid corticosteroids in diabetic patients despite potential benefit in non-diabetics. 1

Common Pitfalls to Avoid

• Do not routinely add MRSA coverage for typical lip cellulitis—reserve MRSA-active agents only for specific high-risk scenarios. 1, 2

• Do not use trimethoprim-sulfamethoxazole or doxycycline as monotherapy, as their activity against beta-hemolytic streptococci is unreliable. 1, 2

• Do not extend treatment beyond 5 days automatically—only extend if clinical improvement has not occurred. 1, 2

• Reassess within 24-48 hours for outpatients to ensure clinical improvement; consider resistant organisms, cellulitis mimickers (contact dermatitis, angioedema), or underlying complications if no improvement occurs. 1, 2

Monitoring Response to Therapy

• Blood cultures are positive in only 5% of cases and are unnecessary for typical lip cellulitis. 1

• Obtain blood cultures and consider tissue cultures only in patients with severe systemic features, malignancy, neutropenia, or unusual predisposing factors. 1

• If the patient fails to improve with appropriate first-line antibiotics within 48-72 hours, immediately add empiric MRSA coverage and consider alternative diagnoses. 1, 5