Management of Inflamed Sebaceous (Epidermoid) Cysts
Acute Treatment: Incision and Drainage
The definitive treatment for an inflamed sebaceous cyst is incision and drainage with thorough evacuation of all purulent material and probing of the cavity to break up loculations, followed by simple dry dressing coverage. 1, 2, 3
Critical Technical Steps
- Make an adequate incision to allow complete evacuation of the cheesy keratinous material and any pus 1
- Probe the cavity thoroughly to break up all loculations and septations—this is the most critical step to prevent treatment failure 1, 4, 3
- Evacuate all contents completely—inadequate initial drainage is the most common cause of persistent drainage and recurrence 4, 2
- Cover with a simple dry dressing only—do not pack the wound with gauze, as packing causes more pain without improving healing 1, 2, 3
Understanding the Pathophysiology
The inflammation in epidermoid cysts occurs as a reaction to rupture of the cyst wall and extrusion of keratinous contents into the dermis, rather than as a primary bacterial infection 1. Even uninflamed cysts contain normal skin flora in their contents, and inflamed cysts yield the same organisms, supporting this mechanism 1.
When to Use Antibiotics
Systemic antibiotics are rarely necessary and should only be used when specific criteria are met. 1, 2, 3
Indications for Antibiotic Therapy
Add antibiotics only when the patient has:
- Temperature >38°C or <36°C 3
- Tachycardia >90 beats per minute 3
- Tachypnea >24 breaths per minute 3
- White blood cell count >12,000 or <4,000 cells/µL 3
- Extensive surrounding cellulitis with erythema extending >5 cm beyond the wound margins with induration 4, 3
- Severely impaired host defenses or immunocompromised state 1, 3
- Multiple lesions or cutaneous gangrene 1
Antibiotic Selection When Indicated
- 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: Typically 5-7 days depending on clinical response 3
Do Not Routinely Culture
Gram stain and culture are not recommended as routine practice for inflamed epidermoid cysts 2, 3. Reserve cultures only for cases with systemic signs of infection, treatment failure, or immunocompromised patients 3.
Management of Treatment Failure
If drainage persists beyond 2-3 weeks or infection worsens, the wound requires re-drainage. 4, 3
Assessment of Persistent Drainage
Most wounds should heal within 2-3 weeks with simple dry dressing changes 4. Persistent drainage beyond this timeframe indicates inadequate initial treatment 4, 3.
Re-Drainage Technique
- Re-open the incision and ensure complete evacuation of all remaining contents 4, 3
- Probe the cavity thoroughly again to break up any remaining loculations or septations 4, 3
- Search for retained foreign material if recurrent problems occur at the same site 4, 2
- Cover with dry dressing—do not pack 4, 3
Definitive Treatment: Complete Excision
For recurrent infections at the same site, perform complete excision of the cyst and its wall once acute inflammation has resolved. 2, 3
Timing of Definitive Excision
The traditional approach involves initial incision and drainage, followed by elective excision 1-2 months later when inflammation has subsided 5. However, one-stage excision during acute inflammation is an alternative approach that some studies suggest may reduce antibiotic exposure and overall morbidity in appropriately selected cases 5.
Alternative Minimally Invasive Approaches
For uninfected or mildly inflamed cysts, particularly in cosmetically sensitive areas, CO2 laser punch-assisted removal of contents followed by cyst wall extraction offers minimal scarring with acceptable recurrence rates (0% for uninfected, 16.7% for infected cysts) 6, 7.
Critical Pitfalls to Avoid
- Never assume ongoing drainage beyond 2-3 weeks is normal healing—this indicates inadequate initial treatment requiring re-drainage 4, 3
- Never prescribe antibiotics without addressing the mechanical problem—antibiotics alone without adequate drainage will fail 4, 3
- Never close the wound without ensuring complete drainage—this leads to recurrent infection 4, 3
- Never pack the wound unnecessarily—this increases pain without improving outcomes 2, 3
- Never routinely culture or prescribe antibiotics in the absence of systemic infection signs 2, 3