Furunculosis – Causes, Symptoms, Diagnosis, Treatment and Ongoing care



Acute bacterial abscess of a hair follicle (often Staphylococcus aureus):

  • System(s) affected: Skin/Exocrine
  • Synonym(s): Boils



  • Predominant age:
    • Adolescents and young adults
    • Clusters have been reported in teenagers living in crowded quarters, within families, or in high school athletes.
  • Predominant sex: Male = Female


Exact data are not available.

Risk Factors

  • Carriage of pathogenic strain of Staphylococcus sp. in nares, skin, axilla, and perineum
  • Rarely, polymorphonuclear leukocyte defect or hyperimmunoglobulin E–Staphylococcus sp. abscess syndrome
  • Diabetes mellitus, malnutrition, alcoholism, obesity, atopic dermatitis
  • Primary immunodeficiency disease and AIDS (common variable immunodeficiency, chronic granulomatous disease, Chediak-Higashi syndrome, C3 deficiency, C3 hypercatabolism, transient hypogammaglobulinemia of infancy, immunodeficiency with thymoma, Wiskott-Aldrich syndrome)
  • Secondary immunodeficiency (e.g., leukemia, leukopenia, neutropenia, therapeutic immunosuppression)
  • Medication impairing neutrophil function (e.g., omeprazole)



General Prevention

Patient education regarding self-care (see General Measures); treatment and prevention are interrelated.


Infection spreads away from hair follicle into surrounding dermis.


Pathogenic strain of S. aureus (usually); increasing incidence of community-acquired methicillin-resistant S. aureus (CA-MRSA)

Commonly Associated Conditions

  • Usually normal immune system
  • Diabetes mellitus
  • Polymorphonuclear leukocyte defect (rare)
  • Hyperimmunoglobulin E–Staphylococcus sp. abscess syndrome (rare)
  • See Risk Factors.

Methicillin-resistant Staphylococcus aureus, Dicloxacillin, Staphylococcus, Antibacterial, wiskott aldrich syndrome, chronic granulomatous disease, thymoma, hypogammaglobulinemia, leukopenia, diabetes mellitus,



  • Located on hair-bearing sites, especially areas prone to friction or repeated minor traumas (e.g., underneath belt, anterior aspects of thighs, nape, buttocks)
  • No initial fever or systemic symptoms
  • The folliculocentric nodule may enlarge, become painful, and develop into an abscess (frequently with spontaneous drainage).

Physical Exam

  • Painful erythematous papules/nodules (1–5 cm) with central pustules
  • Tender, red, perifollicular swelling, terminating in discharge of pus and necrotic plug
  • The lesions may be solitary or clustered.

Diagnostic Tests & Interpretation


Initial lab tests

Culture of the purulent contents

Follow-Up & Special Considerations

  • Immunoglobulin levels in rare (e.g., recurrent or otherwise inexplicable) cases
  • If culture grows gram-negative bacteria or fungus, consider polymorphonuclear neutrophil leukocyte functional defect

Pathological Findings

Histopathology (though a biopsy is rarely needed):

  • Perifollicular necrosis containing fibrinoid material and neutrophils
  • At deep end of necrotic plug, in subcutaneous tissue, is a large abscess with a Gram stain positive for small collections of S. aureus.

Differential Diagnosis

  • Folliculitis
  • Pseudofolliculitis
  • Carbuncles
  • Ruptured epidermal cyst
  • Myiasis (larva of botfly/tumbafly)
  • Hidradenitis suppurativa
  • Atypical bacterial or fungal infections



First Line

  • If suspect CA-MRSA, see Second Line.
  • If abscesses multiple, if lesions have marked surrounding inflammation, cellulitis, systemic symptoms such as fever, or if immunocompromised:
    • Obtain culture, and place on antibiotics directed at S. aureus × 10–14 days.
    • Dicloxacillin (Dynapen, Pathocil) 500 mg p.o. q.i.d. or
    • Cephalexin 250 mg p.o. q.i.d. or
    • Clindamycin 150 mg q.i.d. if penicillin-allergic
  • Suppression of pathogenic strain (if topical treatment fails):
    • Dicloxacillin/cloxacillin 500 mg b.i.d. × 10–14 days
    • Cephalexin or clindamycin (if penicillin-allergic)
    • If preceding fails, dicloxacillin/cloxacillin 500 mg plus rifampin 600 mg p.o. daily × 7–10 days or clindamycin 150 mg/d × 3 months (1)[C]
  • Contraindications: Allergy to the particular drug selected
  • Precautions: Cloxacillin and dicloxacillin: Anaphylactic reaction


Second Line

  • Resistant strains of S. aureus (MRSA): Clindamycin 300 mg q6h or doxycycline 100 mg q12h or TMP-SMX DS 1 tab q8h or minocycline 100 mg q12h (2)[C]
  • If known or suspected impaired neutrophil function (e.g., impaired chemotaxis, phagocytosis, superoxide generation), add vitamin C 1,000 mg/d × 4–6 weeks (prevents oxidation of neutrophils)
  • If fail with antibiotic regimens:
    • May try oral pentoxifylline 400 mg t.i.d. × 2–6 months (3)[C]
    • Contraindications: Recent cerebral and/or retinal hemorrhage; intolerance to methylxanthines (e.g., caffeine, theophylline); allergy to the particular drug selected
    • Precautions: Prolonged prothrombin time (PT) and/or bleeding; if on warfarin, frequent monitoring of PT

Additional Treatment

General Measures

  • Moist, warm compresses (provide comfort, encourage localization/pointing/drainage) 30 minutes q.i.d.
  • If pointing or large, incise and drain
  • Consider packing.
  • Routine culture not necessary for localized abscess in nondiabetic patients with normal immune system
  • Systemic antibiotics usually unnecessary, unless extensive surrounding cellulitis or fever
  • If recurrent, usually related to chronic skin carriage of Staphylococci (nares or on skin). Treatment goals are to decrease or eliminate pathogenic strainor suppress pathogenic strain:
    • Culture nares, skin, axilla, and perineum (culture nares of family members).
    • Apply mupirocin ointment to anterior nares b.i.d. × 5 days (patient and family members/carriers).
    • Culture anterior nares every 3 months. If failure, retreat with mupirocin or consider oral antibiotics (4)[C].
    • See Medications, First Line, Suppression of Pathogenic Strain.
  • Especially in recurrent cases, wash entire body and fingernails (with nailbrush) daily for 1–3 weeks with povidone–iodine (Betadine), hexachlorophene (Hibiclens), or pHisoHex soap (all can cause dry skin)
  • Sanitary practices: Change towels, washcloths, and sheets daily; clean shaving instruments; avoid nose picking; change wound dressings frequently; do not share items of personal hygiene.

Ongoing Care

Follow-Up Recommendations

Patient Monitoring

Instruct patient to see physician if compresses unsuccessful




  • Self-limited: Usually drains pus spontaneously and will heal with or without scarring within several days
  • Recurrent/chronic: May last for months or years


  • Scarring
  • Bacteremia
  • Seeding (e.g., septal/valve defect, arthritic joint)


1. Klempner MS, Styrt B. Prevention of recurrent staphylococcal skin infections with low-dose oral clindamycin therapy. JAMA. 1988;260:2682–5.

2. Up To Date 2007. Impetigo, Folliculitis, Furunculosis, and Carbuncles.

3. Wahba-Yahav AV. Intractable chronic furunculosis: prevention of recurrences with pentoxifylline. Acta Derm Venereol. 1992;72:461–2.

4. Doebbeling BN, et al. Long Term Efficacy of Intranasal Mupirocin, A Prospective Cohort Study of Staphylococcal Aureus. Arch Int Med.1994;154:1505.

5. Winthropp KL, et al. An outbreak of mycobacterium furunculosis associated with footbaths at a nail salon. N Engl J Med. 2002;346(18):1366–71.

Additional Reading

Frazee BW, Lynn J, Charlebois ED, Lambert L, Lowery D, Perdreau-Remington F et al. High prevalence of methicillin-resistant Staphylococcus aureus in emergency department skin and soft tissue infections. Ann Emerg Med.2005;45:311–20.

See Also (Topic, Algorithm, Electronic Media Element)

Folliculitis; Hidradenitis Suppurativa



680.9 Carbuncle and furuncle of unspecified site


40603000 furunculosis of skin and/or subcutaneous tissue (disorder)

Clinical Pearls

  • The pathogens may be different in different localities. Keep up-to-date with the locality-specific epidemiology.
  • If few, furuncles/furunculosis do not always need antibiotic treatment. If systemic symptoms (e.g., fever), cellulitis, or multiple lesions occur, oral antibiotic therapy is needed.
  • Other treatments for MRSA include linezolid p.o. or IV and IV vancomycin.
  • Folliculitis, furunculosis, and carbuncles are parts of a spectrum of pyodermas.
  • Other causative organisms include anaerobic (e.g., Escherichia coli, Pseudomonas aeruginosa, and Streptococcus faecalis), anaerobic (e.g.,Bacteroides, Lactobacillus, Peptobacillius), and Peptostreptococcus), andMycobacteria (5).

Jean-Paul Marat

Many tips are based on recent research, while others were known in ancient times. But they have all been proven to be effective. So keep this website close at hand and make the advice it offers a part of your daily life.

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