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Folliculitis

BASICS

  • Common inflammation of hair follicle
  • Symptoms: pruritus, painless or tender pustules, vesicles, or red papulopustules (≤5 mm)
  • Infectious causes:
  • Bacterial: Staphylococcus aureus (including MRSA), Pseudomonas aeruginosa (hot tubs)
  • Fungal: dermatophytes, Pityrosporum, Candida
  • Viral: VZV, HSV
  • Parasitic: Demodex mites, schistosomes
  • Noninfectious types include acneiform folliculitis, actinic superficial folliculitis, folliculitis decalvans, eosinophilic folliculitis (HIV-associated), and others

EPIDEMIOLOGY

  • Affects all ages, genders, races
  • Higher risk: shaving, diabetes, immunosuppression
  • Prevalence in US approx. 8 per 1,000

ETIOLOGY AND PATHOPHYSIOLOGY

  • Predisposing factors: chronic S. aureus carriage, diabetes, malnutrition, pruritic skin diseases, exposure to contaminated water, occlusive corticosteroids
  • Bacterial infections mainly due to S. aureus, Streptococcus spp., Pseudomonas, Proteus
  • May progress to furuncles or carbuncles
  • Fungal causes include dermatophytic and Pityrosporum infections
  • Viral folliculitis: HSV, molluscum contagiosum
  • Parasitic folliculitis: Demodex folliculorum and schistosomes
  • Acneiform folliculitis induced by drugs (corticosteroids, lithium, EGFR inhibitors)
  • Actinic folliculitis after sun exposure

RISK FACTORS

  • Hair removal (shaving, waxing)
  • Pruritic skin diseases (eczema, scabies)
  • Occlusive clothing/dressings, sweating
  • MRSA exposure or carriage
  • Diabetes mellitus
  • Immunosuppression (HIV, chemotherapy)
  • Use of hot tubs, saunas
  • Chronic antibiotic use

GENERAL PREVENTION

  • Good hygiene: frequent handwashing with antimicrobial soap
  • Wash linens, towels in hot water
  • Proper shaving techniques: exfoliate, shave in direction of hair growth, use single-blade or clippers
  • Avoid shaving affected areas
  • Clean and disinfect shaving instruments daily
  • Monitor hot tub/pool water quality (chlorine, pH)

COMMONLY ASSOCIATED CONDITIONS

  • Impetigo, scabies, acne, follicular psoriasis, eczema, xerosis, S. aureus/MRSA colonization

DIAGNOSIS

History

  • Recent hot tub or pool use, topical corticosteroid use, shaving habits
  • HIV and STD history
  • Timeline and recurrence of lesions

Physical Exam

  • Lesions: 1-5 mm vesicles, pustules, or papules with erythema
  • Distribution: hair-bearing skin—face (beard), proximal limbs, scalp, pubis
  • Pseudomonas folliculitis: widespread rash on trunk and limbs
  • Pseudofolliculitis barbae: hair curls back into skin after shaving

Differential Diagnosis

  • Acne vulgaris and acneiform eruptions
  • Arthropod bites
  • Contact dermatitis
  • Perioral dermatitis
  • Cutaneous candidiasis
  • Milia
  • Atopic dermatitis
  • Follicular psoriasis
  • Hidradenitis suppurativa

Diagnostic Tests

  • Clinical diagnosis based on presentation and history
  • Culture and Gram stain for large or persistent lesions
  • KOH prep and Wood lamp for fungal diagnosis
  • Tzanck smear for suspected HSV folliculitis
  • Ultrasound for deep infections if suspected
  • HIV and syphilis serologies if indicated
  • Blood sugar testing if recurrent or risk factors for diabetes
  • Punch biopsy if uncertain diagnosis or atypical features

TREATMENT

General Measures

  • Lesions usually self-resolve
  • Avoid shaving or waxing affected areas
  • Warm compresses TID
  • Maintain skin hygiene and prevent scratching
  • Antibacterial soaps and bleach baths for prevention

Medication

First Line

  • Staphylococcal folliculitis:
  • Topical mupirocin ointment TID for 10 days
  • Cephalexin 250-500 mg PO QID for 7-10 days
  • Dicloxacillin 250-500 mg PO QID for 7-10 days
  • MRSA suspected:
  • Trimethoprim-sulfamethoxazole DS BID 5-10 days
  • Clindamycin 300 mg PO TID 10-14 days
  • Minocycline 200 mg PO initial, then 100 mg BID for 5-10 days
  • Doxycycline 50-100 mg BID 5-10 days
  • Pseudomonas folliculitis:
  • Topical dilute acetic acid baths
  • Ciprofloxacin 500-750 mg PO BID for 7-14 days (severe)
  • Eosinophilic folliculitis (HIV-associated):
  • HAART for HIV
  • High-potency topical steroids
  • Antihistamines (hydroxyzine, cetirizine)
  • Tacrolimus ointment, isotretinoin cautiously, itraconazole, or metronidazole
  • Fungal folliculitis:
  • Topical antifungals (ketoconazole 2%, selenium sulfide shampoo)
  • Systemic antifungals for relapses (fluconazole, itraconazole, griseofulvin)
  • Parasitic folliculitis:
  • Permethrin 5% topical
  • Ivermectin PO
  • Herpetic folliculitis:
  • Valacyclovir, famciclovir, or acyclovir PO for 5-10 days

Additional Therapies

  • Hot tub and pool testing for chlorine and pH levels

Surgery/Procedures

  • Incision and drainage rarely needed unless abscess develops

ONGOING CARE

  • Follow resistant cases every 2 weeks
  • Monitor for diabetes or immunodeficiency in recurrent/severe cases

DIET

  • Weight reduction in obese patients may reduce skin trauma

PATIENT EDUCATION

  • Avoid shaving in involved areas
  • Monitor hygiene and water quality in hot tubs and pools

PROGNOSIS

  • Usually resolves with treatment
  • Possible recurrence in S. aureus carriers
  • Mupirocin nasal treatment for carriers and household contacts may help

COMPLICATIONS

  • Recurrent folliculitis
  • Scarring and hyperpigmentation
  • Progression to furuncle or abscess

REFERENCES

  1. Khanna N, Chandramohan K, Khaitan BK, et al. Post waxing folliculitis: a clinicopathological evaluation. Int J Dermatol. 2014;53(7):849-854.
  2. Sartelli M, Guirao X, Hardcastle TC, et al. 2018 WSES/SIS-E consensus conference: recommendations for the management of skin and soft-tissue infections. World J Emerg Surg. 2018;13:58.
  3. Lin HS, Lin PT, Tsai YS, et al. Interventions for bacterial folliculitis and boils (furuncles and carbuncles). Cochrane Database Syst Rev. 2021;2(2):CD013099.

CODES

  • ICD10: L73.9 Follicular disorder, unspecified
  • ICD10: L66.2 Folliculitis decalvans
  • ICD10: L73.8 Other specified follicular disorders

CLINICAL PEARLS

  • Folliculitis lesions: 1-5 mm clusters of pruritic erythematous papules/pustules around hair follicles.
  • S. aureus most common cause; consider MRSA coverage based on community prevalence.
  • Educate on hygiene and skin care to prevent recurrence.
  • If no improvement after 2 weeks, consider oral antibiotics or biopsy for confirmation.