What is the recommended antibiotic treatment for a skin infection behind the ear?

Antibiotic Treatment for Skin Infection Behind the Ear

For a skin infection behind the ear, oral antibiotics targeting Staphylococcus aureus and Streptococcus pyogenes are recommended, with cephalexin 500 mg four times daily or dicloxacillin 500 mg four times daily as first-line agents for 7 days. 1

Initial Assessment and Classification

Before prescribing antibiotics, determine if the infection is:

• Purulent (abscess, furuncle): Requires incision and drainage as primary treatment 1
• Non-purulent (cellulitis, erythema): Antibiotics are the mainstay 1
• Presence of systemic signs: Fever, spreading erythema >5 cm, or systemic inflammatory response syndrome (SIRS) indicates more aggressive treatment 1

First-Line Antibiotic Recommendations

For Mild to Moderate Non-Purulent Infections

Oral therapy targeting streptococci and methicillin-susceptible S. aureus (MSSA):

• Cephalexin: 500 mg four times daily for adults; 25 mg/kg/day in 4 divided doses for children 1, 2
• Dicloxacillin: 500 mg four times daily for adults; 25 mg/kg/day in 4 divided doses for children 1
• Amoxicillin-clavulanate: 875/125 mg twice daily for adults; 25 mg/kg/day in 2 divided doses for children 1, 3, 4

Duration: 5-7 days, extending treatment if no improvement within this timeframe 1

Alternative Agents (for penicillin allergy or specific circumstances)

• Clindamycin: 300-450 mg three times daily for adults; 10-20 mg/kg/day in 3 divided doses for children 1, 5
• Erythromycin: 250 mg four times daily (note: some strains may be resistant) 1

When to Consider MRSA Coverage

Add MRSA-active antibiotics if:

• Penetrating trauma to the area 1
• Known MRSA colonization or previous MRSA infection 1
• Injection drug use 1
• Purulent drainage with systemic signs 1
• Failed initial therapy with beta-lactams 1

MRSA-active oral options:

• Trimethoprim-sulfamethoxazole: 1-2 double-strength tablets twice daily 1
• Doxycycline: 100 mg twice daily (avoid in children <8 years) 1
• Clindamycin: 300-450 mg three times daily 1, 5

Purulent Infections (Abscess/Furuncle)

Primary treatment is incision and drainage 1

Antibiotics are indicated only if:

• Systemic signs present (fever, malaise) 1
• Erythema and induration extending >5 cm from wound edge 1
• Multiple lesions 1
• Immunocompromised host 1
• Failed drainage alone 1

If antibiotics are needed after drainage, use MRSA-active agents as community-acquired MRSA is common in purulent infections 1

Important Clinical Pitfalls

• Do not use oral antibiotics for acute otitis externa (swimmer's ear): This requires topical antibiotic drops, not systemic therapy 1
• Cultures are not routinely needed for typical cellulitis without systemic signs 1
• Avoid fluoroquinolones as first-line therapy: Reserve for specific indications or treatment failures 1
• Oral antibiotics have limited utility for purulent infections without drainage 1

Severe Infections Requiring Hospitalization

If the patient has SIRS, rapidly spreading erythema, or appears toxic, immediate IV antibiotics and surgical consultation are warranted 1:

• Vancomycin 15 mg/kg every 12 hours IV PLUS
• Piperacillin-tazobactam 3.375-4.5 g every 6-8 hours IV 1

This broad coverage addresses both MRSA and polymicrobial infections including anaerobes 1

Practical Considerations

• Twice-daily dosing (cephalexin, amoxicillin-clavulanate) improves compliance compared to four-times-daily regimens 6
• Reassess at 48-72 hours: If no improvement, consider MRSA coverage, drainage needs, or alternative diagnosis 1
• Address predisposing factors: Examine interdigital spaces for fungal infection, treat underlying dermatitis, manage edema 1