What is the best course of treatment for an infected acne scar with signs of abscess formation, including swelling, drainage, and intermittent pain?

Management of Infected Acne Scar with Abscess Formation

This patient requires immediate incision and drainage of the abscess, followed by systemic antibiotics and wound care—this is a secondary bacterial infection of an old acne scar, not active acne vulgaris, and must be treated as a skin and soft tissue infection.

Immediate Surgical Management

The primary treatment is incision and drainage (I&D) with thorough evacuation of purulent material. 1 The procedure should include:

• Incision of the fluctuant area with complete drainage of yellowish-white purulent material 1
• Probing the cavity to break up any loculations that may have formed 1
• The wound can be covered with a dry dressing, which is typically the most effective approach, though some clinicians may pack with gauze 1

Systemic Antibiotic Therapy

Systemic antibiotics are indicated due to the presence of surrounding erythema (cellulitis), induration, and drainage. 1 The most appropriate regimen is:

• First-line: Doxycycline 100 mg twice daily for 7-10 days, as it provides excellent coverage for Staphylococcus aureus, the most common pathogen in infected skin lesions 1, 2
• Alternative: Cephalexin 500 mg four times daily if tetracyclines are contraindicated 1
• Consider MRSA coverage if the patient has risk factors (prior MRSA infection, healthcare exposure, or if initial therapy fails) 1

Obtain wound culture at the time of drainage to guide antibiotic therapy if the patient fails to improve within 48-72 hours. 1

Wound Care and Pain Management

• Apply dry dressings changed daily until drainage resolves 1
• Continue the patient's current regimen of ibuprofen and acetaminophen for pain control, as NSAIDs provide appropriate symptomatic relief 3
• Instruct the patient to avoid manipulation of the area, as this increases infection risk 1

Critical Distinction from Acne Vulgaris

This presentation represents a secondary bacterial infection of an old acne scar, not active acne requiring acne-specific therapy. 1 The key distinguishing features are:

• 6-month-old scar that was previously healed 1
• Acute onset of swelling and purulent drainage in the past week 1
• Presence of induration and surrounding erythema consistent with abscess and cellulitis 1

Do not treat this with topical retinoids, benzoyl peroxide, or other acne medications—these are indicated for active acne vulgaris, not for infected scars. 1

Follow-Up Assessment

• Reassess within 48-72 hours to ensure clinical improvement (reduction in erythema, pain, and drainage) 1
• If no improvement or worsening occurs, consider MRSA coverage with trimethoprim-sulfamethoxazole or clindamycin, and review culture results 1
• Once the acute infection resolves, evaluate for any residual scarring that may benefit from scar management techniques 4

Red Flags Requiring Escalation

• Fever, systemic symptoms, or signs of spreading infection warrant more aggressive management 1
• Multiple lesions, extensive cellulitis, or immunocompromised status require broader antibiotic coverage and possible hospitalization 1
• Failure to improve after I&D and appropriate antibiotics should prompt consideration of deeper infection, atypical organisms, or hidradenitis suppurativa 3, 5