Management of Infected Sebaceous (Epidermoid) Cysts
Incision and drainage is the primary treatment for infected epidermoid cysts, and antibiotics are generally not recommended. 1
Primary Treatment Approach
The cornerstone of management is surgical drainage, not antibiotics. The 2014 IDSA guidelines provide a strong recommendation (with moderate-quality evidence) that:
- Gram stain and culture of pus from inflamed epidermoid cysts are NOT recommended 1
- Incision and drainage is the recommended definitive treatment for inflamed epidermoid cysts 1
- Antibiotics play only a subsidiary role and should not be the primary treatment 1
The distinction between cellulitis and purulent collections is clinically crucial: cellulitis requires antibiotics as primary treatment, whereas purulent collections (like infected cysts) require drainage, with antimicrobial therapy either being unnecessary or having only a subsidiary role 1.
When Antibiotics May Be Considered
Adjunctive antibiotics should only be added in specific circumstances:
Indications for Adding Antibiotics 1
- Extensive surrounding cellulitis (erythema >5 cm from the cyst)
- Systemic signs of infection (fever >38°C, tachycardia, hypotension)
- Failed drainage or inability to achieve adequate source control
- Immunocompromised patients
- Presence of MRSA risk factors:
Antibiotic Regimens (When Indicated)
For Typical Cases Without MRSA Risk Factors
Beta-lactam monotherapy is appropriate:
- Cephalexin 500 mg orally every 6 hours for 5 days 1
- Dicloxacillin 250-500 mg orally every 6 hours for 5 days 1
- Extend treatment only if symptoms have not improved within 5 days 1
For Cases With MRSA Risk Factors
MRSA-active therapy is required:
- Clindamycin 300-450 mg orally every 6 hours for 5 days (if local MRSA clindamycin resistance <10%) 1, 2
- Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets twice daily PLUS a beta-lactam (cephalexin or dicloxacin) for 5 days 1
- Doxycycline 100 mg orally twice daily PLUS a beta-lactam for 5 days 1
Critical caveat: Doxycycline or TMP-SMX should NEVER be used as monotherapy for skin infections because they lack reliable activity against beta-hemolytic streptococci 1.
For Severe Infections Requiring Hospitalization
Broad-spectrum IV therapy is mandatory when:
- Signs of systemic toxicity are present 1
- Rapid progression or suspected necrotizing infection 1
- Severe immunocompromise 1
Recommended IV regimens:
- Vancomycin 15-20 mg/kg IV every 8-12 hours PLUS piperacillin-tazobactam 3.375-4.5 g IV every 6 hours 1
- Alternative: Linezolid 600 mg IV twice daily PLUS piperacillin-tazobactam 1, 3
- Duration: 7-14 days based on clinical response 1
Alternative Surgical Approaches
Recent evidence suggests that primary excision of infected cysts may be superior to conventional staged treatment:
- One-stage excision followed by 5 days of antibiotics decreased antibiotic exposure duration, reduced morbidity, and was more economical compared to initial drainage followed by delayed excision 4
- Suture closure after excision of infected tissue with a rim of healthy tissue resulted in quick recovery and eliminated need for frequent dressing changes 5
Common Pitfalls to Avoid
- Do NOT rely on antibiotics alone without drainage – this represents fundamental treatment failure 1
- Do NOT routinely add MRSA coverage unless specific risk factors are present – beta-lactam monotherapy achieves 96% success in typical cases 1
- Do NOT culture inflamed epidermoid cysts routinely – the IDSA specifically recommends against this practice 1
- Do NOT extend antibiotics beyond 5 days based on residual erythema alone – some inflammation persists even after bacterial eradication 1
- Do NOT use doxycycline or TMP-SMX as monotherapy – these agents lack streptococcal coverage 1