What is the best treatment approach for a patient with an infected sebaceous cyst?

Treatment of Infected Sebaceous Cyst

Primary Treatment: Incision and Drainage

Incision and drainage is the definitive treatment for an infected sebaceous cyst, and antibiotics should only be added if systemic signs of infection are present. 1, 2

Procedural Technique

• Perform incision and drainage with thorough evacuation of all purulent material as the cornerstone of treatment 1, 2
• Probe the cavity to break up any loculations or septations to ensure complete drainage—this is a critical technical step that prevents treatment failure 1, 2
• Cover the surgical site with a simple dry dressing after drainage; this approach is effective and evidence-based 1, 2
• Do not pack the wound with gauze—a small study demonstrated that packing causes more pain without improving healing outcomes compared to simple dry dressing 1, 2

Understanding the Pathophysiology

The inflammation in sebaceous cysts typically results from rupture of the cyst wall with extrusion of keratin contents into the dermis, rather than primary bacterial infection, which explains why drainage alone is usually sufficient 1, 2

When to Use Antibiotics

Systemic antibiotics are unnecessary unless specific criteria are met. 3, 1, 2

Indications for Antibiotic Therapy

Add antibiotics only when the patient demonstrates:

• Temperature >38°C or <36°C 1, 2
• Tachycardia >90 beats per minute 1, 2
• Tachypnea >24 breaths per minute 1, 2
• White blood cell count >12,000 or <4,000 cells/µL 1, 2
• Erythema extending >5 cm beyond the wound margins with induration 3
• Markedly impaired host defenses or immunocompromised state 1, 2

Antibiotic Selection

• Choose agents active against Staphylococcus aureus, the most common pathogen 1, 2
• For methicillin-susceptible S. aureus (MSSA): use cephalexin 500 mg every 6 hours orally or cefazolin 1 g every 8 hours IV 3
• For suspected or confirmed MRSA: use vancomycin 15-20 mg/kg every 8-12 hours IV, trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily orally, doxycycline 100 mg twice daily orally, or clindamycin 300-450 mg four times daily orally (if local resistance <10%) 3
• Duration of therapy is typically 5-7 days, depending on clinical response 3

Diagnostic Testing

• Do not routinely perform Gram stain and culture of the pus from infected sebaceous cysts 1, 2
• Cultures should be reserved for cases with systemic signs of infection, treatment failure, or immunocompromised patients 3, 1

Management of Treatment Failure

Signs of Inadequate Drainage

If the infection persists or worsens after initial drainage:

• Re-open the incision and ensure complete evacuation of all contents 1, 2, 4
• Thoroughly probe the cavity again to break up any remaining loculations 1, 2, 4
• Most wounds should heal within 2-3 weeks; persistent drainage beyond this timeframe indicates inadequate initial treatment 4

Recurrent Infections

For recurrent infections at the same site:

• Search for retained foreign material or incomplete cyst wall removal 1, 2, 4
• Consider complete excision of the cyst and its wall once acute inflammation has resolved to prevent future episodes 1, 2

Critical Pitfalls to Avoid

• Never close the wound without adequate drainage—this leads to recurrent infection 1, 2
• Do not routinely prescribe antibiotics in the absence of systemic infection signs 1, 2
• Avoid wound packing—it increases pain without benefit 1, 2
• Do not assume ongoing drainage beyond 2-3 weeks is normal healing—this suggests inadequate initial treatment requiring re-drainage 4
• Do not prescribe antibiotics without addressing the mechanical problem—antibiotics alone without adequate drainage will fail 4