What antibiotics are used to treat an infected skin cyst?

Antibiotics for Infected Skin Cysts

For inflamed epidermoid cysts (skin cysts), incision and drainage is the primary treatment, and antibiotics are NOT routinely recommended unless the patient has systemic signs of infection (fever, tachycardia, elevated white blood cell count) or significant risk factors such as immunosuppression or diabetes. 1

When Antibiotics Are NOT Needed

• Gram stain and culture of pus from inflamed epidermoid cysts are not recommended 1
• Simple inflamed cysts without systemic symptoms should be treated with incision and drainage alone 1, 2
• Studies demonstrate that 85-90% of simple cutaneous abscesses cure with drainage alone, without antibiotics 2
• The inflammation in epidermoid cysts is often a sterile foreign body reaction to keratin rather than true bacterial infection 1

When to Add Antibiotics

Add antibiotics to incision and drainage only when specific risk factors are present 1, 2:

• Systemic inflammatory response syndrome (SIRS): Temperature >38°C or <36°C, heart rate >90 bpm, respiratory rate >24 breaths/min, or WBC >12,000 or <4,000 cells/µL 1
• Severe or extensive disease with rapid progression and associated cellulitis 2
• Immunocompromised patients (diabetes, HIV, immunosuppressive medications) 1, 2
• Extremes of age 2
• Difficult-to-drain abscess locations 2
• Lack of response to incision and drainage alone 2

Antibiotic Selection When Indicated

First-Line Oral Options (for MRSA coverage):

• Trimethoprim-sulfamethoxazole (TMP-SMX): 160-800 mg twice daily 1, 2
• Doxycycline: 100 mg twice daily 1, 2
• Clindamycin: 300-450 mg three times daily 1, 2

Alternative Oral Options (if MRSA not suspected):

• Cephalexin: 500 mg four times daily 1, 2
• Dicloxacillin: 500 mg four times daily 1

Intravenous Options (for severe infections with SIRS):

• Vancomycin 1
• Linezolid 1
• Daptomycin: 10 mg/kg/dose IV once daily 1
• Ceftaroline 1

Duration of Therapy

• 7-10 days is the standard duration when antibiotics are used 1, 2
• Duration should be based on clinical response rather than arbitrary timeframes 2
• Switch from IV to oral when clinical stability is achieved 1

Critical Clinical Pitfalls

The most common error is prescribing antibiotics unnecessarily for inflamed epidermoid cysts. Survey data shows that 84-94% of physicians prescribe antibiotics for inflamed cysts despite lack of evidence supporting this practice 3. This contributes to antibiotic resistance and unnecessary costs without improving outcomes 3.

Remember: The inflammation in epidermoid cysts is typically a sterile inflammatory reaction to ruptured keratin contents, not bacterial infection 1. Even when Staphylococcus aureus is present, incision and drainage alone achieves cure rates of 85-90% 2, 4.