Folliculitis

Folliculitis is an inflammatory and infectious disorder of the hair follicle, most commonly caused by Staphylococcus aureus. It may also be caused by Gram-negative bacteria such as Pseudomonas aeruginosa, fungi such as Candida albicans and dermatophytes, parasites such as Demodex mites, and rarely viruses such as herpes simplex virus (HSV). The disease represents a spectrum ranging from superficial follicular inflammation to deep destructive infections such as furuncles (boils) and carbuncles.

The condition develops when microorganisms invade the hair follicle following occlusion, friction, maceration, shaving, or immunosuppression.

Etiology

Infectious causes

• Staphylococcus aureus – most common cause of acute folliculitis, furuncles, and carbuncles.

• Pseudomonas aeruginosa – associated with hot tubs and swimming pools (hot-tub folliculitis).

• Candida albicans – commonly affects moist areas and patients with diabetes.

• Dermatophytes – fungal folliculitis, particularly in immunocompromised individuals.

• Demodex mites – parasitic folliculitis, mainly involving the face.

• Herpes simplex virus (HSV) – rare cause of viral folliculitis.

Non-infectious causes

• Shaving (pseudo-folliculitis barbae).

• Occlusive clothing.

• Oils and cosmetics.

• Topical corticosteroids.

• Friction (e.g. athletes, soldiers).

• Hyperhidrosis.

• Obesity.

• Diabetes mellitus.

• HIV/AIDS and other immunocompromised states.

• Prolonged antibiotic use.

Pathophysiology

The disease progresses through:

• Disruption of the follicular barrier.

• Microbial invasion of the follicular opening.

• Neutrophilic inflammation.

• Pus formation.

• Follicular rupture leading to dermal necrosis and scarring in deep disease.

Disease progression:

• Folliculitis → Furuncle (boil) → Carbuncle.

Clinical classification

Superficial folliculitis

• Infection limited to the epidermal portion of the hair follicle.

• Small follicular pustules.

Deep folliculitis

• Infection extends into the dermis.

• Painful inflammatory nodules.

Furuncle (boil)

• Deep infection of a single hair follicle.

• Central necrotic core.

Carbuncle

• Coalescence of multiple infected follicles.

• Multiple draining sinuses with systemic symptoms.

Pseudo-folliculitis

• Non-infectious inflammation caused by ingrown hairs, commonly affecting the beard area.

Clinical presentation

Clinical features depend on the underlying cause and severity of disease and may progress to pseudo-folliculitis, furuncles, or carbuncles.

Superficial disease

• Scattered or extensive follicular pustules.

• Macular or papulo-erythematous lesions.

• Papules and pustules.

• Mild itching.

• Lesions commonly occur on the thighs, buttocks, back, scalp, trunk, and bearded area.

Deep disease

• Firm, broad, swollen, painful, fluctuant deep nodules.

• Necrosis and suppuration with discharge of a necrotic core.

• Surrounding cellulitis.

• Multiple drainage tracts.

• Fever.

• General body malaise.

Chronic or complicated disease

• Post-inflammatory hyperpigmentation.

• Permanent scars.

• Scarring alopecia.

• Keloids.

• Recurrent abscesses.

Diagnosis

Folliculitis is primarily a clinical diagnosis based on:

• Follicle-centered pustules.

• Erythematous papules.

• Presence of a central hair shaft.

• Pain or itching.

• Possible purulent discharge.

• Systemic symptoms in severe disease.

Investigations

Investigations are usually unnecessary in uncomplicated disease but should be considered in recurrent, severe, or treatment-resistant cases.

Possible investigations include:

• Pus swab for culture and antimicrobial sensitivity.

• Gram stain.

• Potassium hydroxide (KOH) preparation to identify fungal infection.

• Blood glucose testing to screen for diabetes mellitus.

• HIV testing in recurrent or severe disease.

• Nasal swab to detect Staphylococcus aureus or MRSA carriage.

Differential diagnosis

• Acne vulgaris.

• Impetigo.

• Hidradenitis suppurativa.

• Scabies.

• Insect bites.

• Contact dermatitis.

• Herpes simplex infection.

• Cutaneous candidiasis.

Management

Management depends on disease severity and the underlying cause.

Non-pharmacological treatment

• Avoid suspected irritants and friction.

• Improve personal hygiene.

• Clean affected skin with soap and water.

• Wear loose-fitting clothing.

• Apply warm compresses 3–4 times daily.

• Control diabetes where present.

• Weight reduction in obese individuals.

For pseudo-folliculitis of the beard:

• Stop shaving for several weeks until improvement occurs.

• Allow hair to grow to at least 1 mm in length.

• Shaving with electric razors or clippers is preferred over manual razors.

• Avoid close shaving.

Pharmacological treatment

Mild localized bacterial folliculitis

Potassium permanganate (PP) soaks

• 1:40,000 (0.025%) solution.

• Apply every 12 hours for 3–4 days.

• Each session should last 15–20 minutes.

Apply one of the following topical agents:

• Gentian violet paint (topical) 0.5% every 12 hours for 5 days.

OR

• Mupirocin (topical) 2% every 12 hours for 7–14 days.

OR

• Fusidic acid (topical) 2% every 12 hours for 7–14 days.

Moderate or severe bacterial folliculitis

Systemic antibiotics are indicated in patients with:

• Fever or systemic symptoms.

• Extensive lesions.

• Furuncle or carbuncle.

• Recurrent disease.

• Immunocompromised state.

• Failure of topical therapy.

Oral antibiotic options include:

• Phenoxymethylpenicillin:

  • Adults: 500 mg orally every 6 hours for 7 days.

  • Children: 25 mg/kg orally every 6 hours for 7 days.

OR

• Erythromycin:

  • Adults: 500 mg orally every 8 hours for 10 days.

  • Children: 25–50 mg/kg orally every 8 hours for 10 days.

OR

• Amoxicillin + clavulanic acid 625 mg orally every 8 hours for 5 days.

Fungal folliculitis

• Clotrimazole cream (topical) every 12 hours for 4 weeks.

OR

• Miconazole cream (topical) every 12 hours for 4 weeks.

Incision and drainage

Incision and drainage should be performed for:

• Furuncles.

• Carbuncles.

• Abscesses.

Antibiotics alone are insufficient when significant pus collection is present.

Complications

Untreated or severe folliculitis may result in:

• Furuncle formation.

• Carbuncle formation.

• Abscess formation.

• Cellulitis.

• Multiple drainage sinuses.

• Scarring alopecia.

• Permanent scarring.

• Post-inflammatory hyperpigmentation.

• Keloid formation.

• Chronic recurrent furunculosis.

• Sepsis (rare).

Prevention

• Maintain good personal hygiene.

• Wash skin regularly with soap and water.

• Avoid sharing towels, clothing, and razors.

• Use proper shaving techniques.

• Keep skin clean and dry.

• Avoid tight-fitting clothing.

• Control diabetes mellitus.

• Treat nasal Staphylococcus aureus carriers in recurrent infections where appropriate.

• Avoid contaminated swimming pools and hot tubs.

• Treat minor skin lesions promptly.

Prognosis