Skin nontumor

Infectious disorders


Author: Ha Kirsten Do

Last author update: 1 September 2010
Last staff update: 25 April 2024 (update in progress)

Copyright: 2002-2024,, Inc.

PubMed Search: Folliculitis [title]

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Cite this page: Do HK. Folliculitis. website. Accessed May 20th, 2024.
Definition / general
  • Primary inflammation of a hair follicle, either infectious or noninfectious
  • Perifolliculitis: presence of inflammatory cells in the perifollicular tissues that may involve the adjacent reticular dermis; either primarily lymphocytic (lichen planopilaris, pityriasis rubra pilaris) or granulomatous (perioral dermatitis, rosacea)

  • Pseudolymphomatous folliculitis: facial lesion with dense, polymorphic, mixed lymphocytes around hair follicles and infiltrating follicular epithelium
  • Common sites are the face, scalp, thighs, axilla and inguinal area
  • Caused by infection, friction and other causes of follicular trauma, excessive perspiration and occlusion
  • Infectious cases are either superficial (fungi, bacteria, syphilis, viral) or deep (usually granulomatous and due to either fungi or bacteria)
  • Fungal forms may be endothrix (spores are within hair shaft) or ectothrix (spores are on outer surface of hair shaft)
  • Noninfectious cases are either superficial / suppurative (acne vulgaris, rosacea, follicular mucinosis, steroid induced), deep / granulomatous (acne vulgaris-conglobate and keloidal forms or perforating) or spongiotic (Fox-Fordyce disease, atopic dermatitis, pruritic folliculitis of pregnancy)
  • Epidermal growth factor receptor (EGFR) inhibitors appear to be relevant in folliculitis by causing abnormal epidermal differentiation that leads to follicular obstruction and subsequent inflammation (Br J Dermatol 2001;144:1169)
Clinical features
  • Superficial folliculitis is more common but is often self-limited
  • Patients with recurrent or persistent superficial folliculitis or with deep folliculitis are more likely to seek medical care
  • In recalcitrant folliculitis that failed standard therapy, consider cultures for sensitivity, Gram stain, potassium chloride (KOH) preparation to rule out fungal folliculitis
  • Clinical presentation of superficial folliculitis is acute onset of mildy tender papules and pustules
  • Deep folliculitis is usually associated with more pain and may have suppurative drainage; may cause scarring and permanent hair loss
  • For uncomplicated superficial folliculitis, use antibacterial soaps, good handwashing
  • For recurrent and deep lesions, treat empirically with topical antibiotics
  • Antiobiotics should kill Staphylococcus aureus, the most common pathogen; recommended to use dicloxacillin and cephalosporins (eMedicine)
  • For MRSA, use clindamycin, bactrim, minocycline or linezolid
  • For Staphylococcus aureus carriers, treat patient and family with mupirocin ointment BID x 5 days or rifampin 600 mg/day x 10 days
Clinical images

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Microscopic (histologic) description
  • Superficial folliculitis has moderate inflammatory cells in the follicular ostium and upper regions of the follicle
  • Infiltrate initially consists of neutrophils, later becomes more mixed with lymphocytes and macrophages
Microscopic (histologic) images

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Micro image of folliculitis

Differential diagnosis
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