What is the recommended treatment for a patient with a boil (furuncle) under the arm?

Treatment for Boil Under Arm

Incision and drainage is the primary treatment for a boil (furuncle) under the arm, and antibiotics are NOT routinely needed unless you have fever, extensive surrounding redness, multiple boils, or are immunocompromised. 1

Initial Management Based on Size

For small boils:

• Apply warm, moist compresses several times daily to promote spontaneous drainage 1, 2
• This achieves an 85-90% cure rate with drainage alone, regardless of antibiotic use 2, 3
• The moist heat brings the infection to a head and facilitates natural drainage without surgery 4

For large boils:

• Incision and drainage is the definitive treatment (strong recommendation, high-quality evidence) 1
• After drainage, cover the wound with a dry sterile dressing 1
• Do NOT pack the wound with gauze—packing causes more pain without improving healing 1, 2

When to Add Antibiotics

Antibiotics are indicated ONLY if any of these conditions are present: 1

• Fever (temperature >38°C or <36°C) 1
• Signs of systemic inflammatory response syndrome (SIRS): tachypnea >24 breaths/minute, tachycardia >90 beats/minute, or white blood cell count >12,000 or <400 cells/µL 1
• Extensive surrounding cellulitis beyond the immediate abscess area 1
• Multiple lesions 1, 2
• Immunocompromised status (diabetes, HIV, chemotherapy, or other markedly impaired host defenses) 1, 2

If antibiotics are needed, choose agents active against MRSA: 1, 2, 3

• Trimethoprim-sulfamethoxazole 2, 3
• Doxycycline 2, 3
• Clindamycin 2, 3
• Alternative: Cephalexin or dicloxacillin if MRSA is not suspected 3

Culture Recommendations

• Culture is recommended for carbuncles and abscesses, but treatment without culture is reasonable in typical cases 1
• Gram stain and culture are NOT needed for simple, uncomplicated boils 1
• Culture is strongly recommended for recurrent boils to identify the causative organism 1, 2

Prevention of Recurrence

If you experience recurrent boils, implement decolonization measures: 1, 2

• Intranasal mupirocin 2% ointment twice daily for 5 days (reduces recurrences by ~50%) 1, 2, 4
• Daily chlorhexidine body washes for 5-14 days 1, 2, 4
• Daily decontamination of personal items: towels, sheets, and clothes 1, 2
• Avoid sharing personal items and use separate towels/washcloths 2, 4
• Clean surfaces that contact bare skin daily 2

For recurrent disease, also consider: 1, 2

• Searching for local anatomic causes: pilonidal cyst, hidradenitis suppurativa, or foreign material 1, 2
• Evaluating household members for S. aureus colonization if ongoing transmission is suspected 2, 3
• A 5-10 day course of antibiotics active against the isolated pathogen 1

Important Caveats

• Nasal colonization with S. aureus is the primary predisposing factor for recurrent boils in most individuals 1, 2
• Needle aspiration is NOT recommended—it has only a 25% success rate overall and <10% success with MRSA infections 1
• Evaluation for neutrophil disorders is only needed if recurrent abscesses began in early childhood, not for adult-onset disease 1, 2
• The axilla (underarm) is a common site for boils due to hair follicles, friction, and moisture 1, 5