What is folliculitis, its causes, symptoms, and treatment options?

Folliculitis: Definition, Causes, Symptoms, and Treatment

Folliculitis is a superficial inflammatory condition of the hair follicle where inflammation and pus remain limited to the epidermis, distinguishing it from deeper infections like furuncles (boils) where suppuration extends through the dermis into subcutaneous tissue. 1, 2

Clinical Definition and Anatomical Location

• Folliculitis involves the superficial aspect of the hair follicle, specifically affecting the infundibulum (superficial part outlined by the sebaceous duct) and can involve the follicular opening or perifollicular structures 3
• The condition manifests as 1mm-wide vesicles, pustules, or papulopustules in acute cases, while chronic cases show hyperkeratosis and keratotic plug formations 3
• The key distinguishing feature is that pus remains in the epidermis, whereas furuncles extend deeper with abscess formation in subcutaneous tissue 1

Causative Agents

• Staphylococcus aureus is the most common causative organism, identified in approximately 18-26% of cases when microbes are directly visualized in inflamed follicles 4, 5
• Other bacterial causes include Gram-negative organisms, while fungal (8% of cases), parasitic, and viral pathogens can also produce follicular papules and pustules 4, 5
• Importantly, superficial pustules do not always indicate infection—many cases are noninfectious in origin, making cytology or culture essential before assuming bacterial etiology 3, 4
• Propionibacterium acnes has been identified in some cases, often forming macrocolonies or biofilm structures 5

Clinical Presentation

• Lesions appear as small inflammatory papules, pustules, or papulopustules centered around hair follicles 3
• The condition can occur on any hairy skin surface 1
• Each lesion typically consists of an inflammatory reaction with an overlying pustule through which hair may emerge 1
• Chronic folliculitis shows hyperkeratotic changes and keratotic plugging rather than acute pustulation 3

Treatment Algorithm

First-Line Therapy for Mild, Localized Folliculitis

• Apply topical clindamycin 1% solution or gel twice daily for 12 weeks as initial treatment 2
• This approach targets the most common bacterial cause (S. aureus) while avoiding systemic antibiotic exposure 2

Escalation for Moderate to Severe or Widespread Disease

• If inadequate response after 4-6 weeks of topical therapy, switch to oral tetracycline 500 mg twice daily for 4 months 2
• Avoid tetracyclines in children under 8 years of age due to risk of dental staining and bone growth effects 2
• Alternative systemic options include other tetracycline derivatives (doxycycline, minocycline) for their anti-inflammatory properties 1

When to Consider MRSA Coverage

• Use antibiotics with MRSA coverage (trimethoprim-sulfamethoxazole, doxycycline, or clindamycin) for suspected or confirmed MRSA infections 2
• This is particularly important in settings with high MRSA prevalence or when initial therapy fails 2
• Treatment duration should be 5-10 days initially, extending only if no improvement occurs 2

Diagnostic Approach

• Cytology is a simple, rapid, inexpensive, and repeatable first-line diagnostic method that can reveal bacterial, fungal, viral, and parasitic pathogens 4
• Gram stain and culture should be obtained when systemic treatment is contemplated or when lesions are recurrent 1
• Histologic confirmation may be needed when clinical appearance is atypical or diagnosis is uncertain 6

Critical Distinctions to Avoid Mismanagement

• Do not confuse folliculitis with furuncles or carbuncles—the latter require incision and drainage as primary treatment, while folliculitis is managed medically 1, 2, 7
• Avoid empiric antibacterial treatment for months without confirming bacterial etiology, as many cases are noninfectious and prolonged unnecessary antibiotic use promotes resistance 4
• Do not use topical steroids on infected folliculitis, as they may worsen the condition 2
• Greasy creams should be avoided for basic care as they may facilitate folliculitis development through occlusive properties 1

Management of Recurrent Folliculitis

• Search for predisposing factors including nasal S. aureus colonization (present in 20-40% of general population), poor hygiene, or mechanical factors 1
• Consider a 5-day decolonization regimen including intranasal mupirocin twice daily, daily chlorhexidine washes, and decontamination of personal items (towels, sheets, clothing) 1, 2
• For recurrent cases with confirmed nasal colonization, mupirocin ointment applied twice daily in anterior nares for the first 5 days each month reduces recurrences by approximately 50% 1

Preventive Measures

• Use gentle, pH-neutral soaps and tepid water for bathing 1
• Pat skin dry rather than rubbing to avoid follicular trauma 1
• Wear fine cotton clothing instead of synthetic materials that trap moisture 1
• Shave carefully to avoid follicular injury 1
• Maintain separate use of towels and washcloths in outbreak settings 1