What is the diagnosis and treatment for folliculitis, a condition affecting hair follicles, potentially caused by bacterial, fungal, or viral infections?

Folliculitis: Definition and Treatment

Folliculitis is a superficial infection of the hair follicle where inflammation is limited to the epidermis with pus present in the epidermis, most commonly caused by Staphylococcus aureus, and differs from deeper infections like furuncles where suppuration extends through the dermis into subcutaneous tissue. 1

Clinical Presentation

Folliculitis manifests as inflammatory lesions at hair follicle sites with the following characteristics:

• Superficial pustules centered on hair follicles with surrounding erythema 1
• Pus confined to the epidermis, distinguishing it from deeper follicular infections 1
• Can occur on any hair-bearing skin surface 1
• May present as scattered pustules or low-grade folliculitis with patchy alopecia in scalp involvement 1

Microbiology

The causative organisms include:

• Bacterial: Staphylococcus aureus is the predominant pathogen (identified in 18% of inflamed follicles in one study), with Propionibacterium acnes less commonly involved 2
• Fungal: Dermatophyte fungi (Microsporum and Trichophyton species) cause follicular involvement in tinea capitis, presenting with diffuse pustular patterns 1
• Viral: Herpes simplex, herpes zoster, and molluscum contagiosum can cause folliculitis, particularly in cases refractory to antibacterial therapy 3
• Approximately one-third of clinically diagnosed non-infectious folliculitis cases show microbial colonization, with bacteria forming macrocolonies or biofilm structures 2

Treatment Algorithm

Simple/Superficial Folliculitis

For uncomplicated folliculitis without systemic signs:

1. First-line nonantibiotic treatment: Topical benzoyl peroxide 4

2. Topical antibiotic options if benzoyl peroxide fails:

   • Mupirocin ointment 4
   • Clindamycin 4

3. Oral antibiotics for treatment-resistant cases:

   • Cephalexin 5, 4
   • Dicloxacillin 4
   • Duration: 5-10 days 1

Important Clinical Distinctions

Do NOT use systemic antibiotics routinely for simple folliculitis unless:

• Extensive surrounding cellulitis develops 1
• Fever or systemic signs of infection present 1
• Multiple lesions with systemic inflammatory response syndrome (SIRS): temperature >38°C or <36°C, tachypnea >24 breaths/minute, tachycardia >90 beats/minute, or WBC >12,000 or <4,000 cells/µL 1
• Markedly impaired host defenses 1

Recurrent Folliculitis Management

For patients with repeated episodes:

1. Culture the lesion early in the course to identify the pathogen 1, 4

2. Decolonization regimen for recurrent S. aureus infection (5-day course):

   • Intranasal mupirocin ointment twice daily for first 5 days each month (reduces recurrences by ~50%) 1
   • Daily chlorhexidine body washes 1
   • Daily decontamination of personal items (towels, sheets, clothing) 1

3. Systemic therapy for persistent cases:

   • Clindamycin 150 mg orally once daily for 3 months (decreases subsequent infections by ~80% for susceptible organisms) 1

Special Considerations

Fungal folliculitis (tinea capitis with follicular involvement):

• Requires systemic antifungal therapy, not topical treatment alone 1
• Laboratory confirmation with culture is advisable to identify causative organism 1

Viral folliculitis:

• Consider viral etiology in cases refractory to antibacterial or antifungal therapy 3
• May require antiviral therapy depending on the causative agent 3

MRSA coverage: Consider for patients with infections not improving with standard treatment, particularly in outbreak settings or with known MRSA colonization 1

Common Pitfalls

• Avoid confusing folliculitis with furuncles: Furuncles extend deeper through the dermis into subcutaneous tissue forming small abscesses and require incision and drainage 1
• Do not overlook fungal or viral causes in treatment-resistant cases 3
• Gram stain and culture are not routinely necessary for typical folliculitis but should be obtained for recurrent cases 1, 4
• Simple folliculitis is often self-limited and may not require antibiotic therapy 4