Folliculitis

Inflammation of the hair follicle, infectious or non-infectious. It is common at every age and affects the beard area, scalp, axillae, buttocks, thighs and trunk.

• Superficial folliculitis involves the follicular ostium (Bockhart impetigo, a pustule with a hair at its centre). Deep folliculitis involves the whole follicle and progresses to furuncles (sycosis barbae in the beard).
• Causes:
  • Staphylococcus aureus is the commonest infectious cause.
  • Pseudomonas aeruginosa causes hot tub folliculitis, from contaminated water 8 to 48 hours earlier.
  • Gram negative folliculitis (Klebsiella, Enterobacter, Proteus) occurs in acne patients on long term oral antibiotics.
  • Malassezia (Pityrosporum) folliculitis causes monomorphic itchy papules on the upper trunk and shoulders.
  • Dermatophytes (Majocchi granuloma) and Candida in occlusion.
  • Demodex.
  • Eosinophilic folliculitis in advanced HIV (CD4 below 250 cells/mm3).
  • Non-infectious: shaving, occlusion, topical steroids, oils, epidermal growth factor receptor inhibitors, lithium and corticosteroids.
• Risk factors: shaving, tight clothing, hot humid conditions, diabetes, obesity, atopic dermatitis, immunosuppression and nasal carriage of S. aureus (20 to 30% of adults).

• Small dome shaped follicular pustules on an erythematous base, 2 to 5 mm, often with a central hair. They are tender or itchy and heal within 7 to 10 days without scarring if superficial.
• Deep folliculitis produces firm, painful nodules, perifollicular abscesses and, in the beard, hair loss and scarring.
• Pseudomonas folliculitis: itchy or tender pink papules and pustules in the areas covered by the swimsuit, sometimes with fever, malaise, sore throat or breast tenderness, resolving in 7 to 14 days.
• Malassezia folliculitis: uniform, itchy, dome shaped papules and pustules over the chest, back, upper arms and face, worse with sweating.
• Eosinophilic folliculitis: intensely itchy urticarial papules on the face, neck and trunk, with eosinophilia.
• Differential diagnosis: acne vulgaris, pseudofolliculitis barbae, keratosis pilaris, miliaria, tinea barbae, scabies, impetigo, folliculitis decalvans, disseminated candidiasis and drug eruptions.
• Complications: furunculosis, abscess, cellulitis, permanent hair loss (folliculitis decalvans, tinea or deep sycosis) and post-inflammatory hyperpigmentation.

• Clinical. Culture a pustule for persistent, widespread or recurrent disease, or where the patient is immunocompromised. Gram stain and bacterial culture with sensitivities identify MRSA.
• Potassium hydroxide preparation or fungal culture where dermatophyte or Malassezia is possible. Yeasts and buds are seen on a smear from an expressed follicular plug.
• Skin biopsy for an unclear or non-responding eruption.
• Take a nasal swab if recurrent staphylococcal disease is suspected.
• Check fasting glucose or HbA1c, and test for HIV in persistent, atypical or severe eosinophilic disease. Full blood count with differential for eosinophilia.

• Remove the cause: stop or change shaving technique (shave with the grain, a single pass, a sharp blade, short intervals), avoid occlusive clothing and oily creams, and shower after sweating or swimming.
• Mild superficial staphylococcal folliculitis:
  • Chlorhexidine 2 to 4% wash once daily for 5 to 7 days, or benzoyl peroxide 5 to 10% wash daily.
  • Mupirocin 2% ointment three times daily for 5 to 7 days, or clindamycin 1% lotion twice daily for 7 to 10 days.
  • Fusidic acid 2% cream is an alternative but resistance is common.
• Extensive, deep or recurrent staphylococcal folliculitis:
  • Flucloxacillin 500 mg orally 6 hourly for 7 to 10 days (child 12.5 to 25 mg/kg 6 hourly).
  • Cefalexin 500 mg orally 6 hourly for 7 to 10 days.
  • Doxycycline 100 mg orally 12 hourly for 7 to 14 days (not in pregnancy or under 8 years).
  • Suspected or proven MRSA: co-trimoxazole 160/800 mg, 1 to 2 tablets 12 hourly, or clindamycin 300 to 450 mg orally 8 hourly.
  • Beard sycosis often needs 2 to 4 weeks of oral therapy.
• Hot tub (Pseudomonas) folliculitis: it is self-limiting. Treat with a topical antiseptic wash and discard or disinfect contaminated floats and swimwear. For severe, prolonged or immunocompromised cases give ciprofloxacin 500 mg orally 12 hourly for 7 days (not in pregnancy or children).
• Malassezia folliculitis:
  • Ketoconazole 2% shampoo applied as a body wash for 5 minutes daily for 2 to 4 weeks, or selenium sulphide 2.5% for 10 minutes daily.
  • Moderate to severe: itraconazole 200 mg orally daily for 7 to 14 days, or fluconazole 100 to 200 mg orally daily for 2 to 4 weeks. Monitor liver tests with courses beyond 2 weeks.
  • Maintenance once or twice weekly with the topical wash prevents relapse.
• Gram negative folliculitis: stop the long term antibiotic, treat with isotretinoin 0.5 mg/kg per day for 4 to 6 months if acne is severe (contraindicated in pregnancy), or use a Gram-negative-active antibiotic such as ciprofloxacin guided by culture.
• Eosinophilic folliculitis in HIV: start or optimise antiretroviral therapy, apply a potent topical corticosteroid (betamethasone valerate 0.1% once or twice daily), give a non-sedating antihistamine, and consider indomethacin 25 mg orally three times daily. Phototherapy is used for refractory disease.
• Recurrent staphylococcal folliculitis, with decolonisation:
  • Mupirocin 2% intranasal twice daily for 5 days.
  • Chlorhexidine 4% body wash daily for 5 to 14 days, avoiding the eyes and ears.
  • Wash towels, bedding and clothes at 60 C or hotter, and replace razors.
  • Treat household members who carry the organism.
  • Rifampicin with a second drug is used for refractory carriage but evidence is limited.
• Special groups:
  • Pregnancy: use topical mupirocin, flucloxacillin or cefalexin. Avoid doxycycline, ciprofloxacin and oral azoles.
  • Children: avoid doxycycline under 8 years.
  • Diabetes and immunosuppression: treat early, take cultures, and escalate to oral therapy sooner.
• Follow up: review at 1 to 2 weeks. Refer to dermatology when there is scarring, hair loss, no response in 4 weeks, or suspicion of folliculitis decalvans, dissecting cellulitis or fungal infection.