> Table of Contents > Impetigo
Elisabeth L. Backer, MD
image BASICS
  • A contagious, superficial, intraepidermal infection occurring prominently on exposed areas of the face and extremities, most often seen in children
  • Infected patients usually have multiple lesions.
  • Cultures are positive in >80% cases for Staphylococcus aureus either alone or combined with group A &bgr;-hemolytic streptococci; S. aureus is the more common pathogen since the 1990s.
  • Nonbullous impetigo: most common form of impetigo. Formation of vesiculopustules that rupture, leading to crusting with a characteristic golden appearance; local lymphadenopathy may occur.
  • Bullous impetigo: staphylococcal impetigo that progresses rapidly from small to large flaccid bullae (newborns/young children) caused by epidermolytic toxin release; less lymphadenopathy; trunk more often affected; <30% of patients
  • Folliculitis: considered by some to be S. aureus impetigo of hair follicles
  • Ecthyma: a deeper, ulcerated impetigo infection often with lymphadenitis
  • System(s) affected: skin/exocrine
  • Synonym(s): pyoderma; impetigo contagiosa; impetigo vulgaris; fox impetigo
  • Predominant sex: male = female
  • Predominant age: children ages 2 to 5 years
In the United States: not reported but common
Pediatric Considerations
  • Poststreptococcal glomerulonephritis may follow impetigo (in young children).
  • Impetigo neonatorum may occur due to nursery contamination.
  • Coagulase-positive staphylococci: pure culture ˜50-90%; more contagious via contact
  • &bgr;-Hemolytic streptococci: pure culture only ˜10% of the time (primarily group A)
  • Mixed infections of streptococci and staphylococci are common; data suggest increasing importance of staphylococci over the past 20 years.
  • Direct contact or insect vector
  • Can result from contamination at trauma site
  • Regional lymphadenopathy
  • Warm, humid environment
  • Tropical or subtropical climate
  • Summer or fall season
  • Minor trauma, insect bites, breaches in skin
  • Poor hygiene, poverty, crowding, epidemics, wartime
  • Familial spread
  • Poor health with anemia and malnutrition
  • Complication of pediculosis, scabies, chickenpox, eczema/atopic dermatitis
  • Contact dermatitis (Rhus spp.)
  • Burns
  • Contact sports
  • Children in daycare
  • Possibly tobacco exposure
  • Carriage of group A Streptococcus and Staphylococcus aureus
  • Close attention to family hygiene, particularly hand washing among children
  • Covering of wounds
  • Avoidance of crowding and sharing of personal items
  • Treatment of atopic dermatitis
  • Malnutrition and anemia
  • Crowded living conditions
  • Poor hygiene
  • Neglected minor trauma
  • Any chronic/underlying dermatitis
  • Tender red macules or papules as early lesions (contact dermatitis presents with pruritic lesions)
  • Thin-roofed vesicles to bullae: usually nontender
  • Pustules
  • Weeping, shallow, red ulcers
  • Honey-colored crusts
  • Satellite lesions
  • Often multiple sites
  • Bullae on buttocks, trunk, face
  • Nonbullous
    • Contact dermatitis
    • Chickenpox
    • Herpes
    • Folliculitis
    • Erysipelas
    • Insect bites
    • Severe eczematous dermatitis
    • Scabies
    • Tinea corporis
  • Bullous
    • Burns
    • Pemphigus vulgaris
    • Bullous pemphigoid
  • Stevens-Johnson syndrome
Initial Tests (lab, imaging)
  • None usually done; cultures of pus/bullae fluid may be helpful if no response to empiric therapy.
    • Culture: taken from the base of lesion after removal of crust will grow both staphylococci and group A streptococci
    • Antistreptolysin-O (ASO) titer: can be weak positive for streptococci but overall not useful
    • Antideoxyribonuclease B (anti-DNase B) and antihyaluronidase (AHT) response more reliable than ASO response
    • Streptozyme: positive for streptococci
  • Disorders that may alter lab results: Streptococcal pharyngitis will alter streptococcal enzyme tests.
Follow-Up Tests & Special Considerations
  • Monitor for spread of disease and systemic manifestations.
  • Serologic testing is helpful in context of impetigo with subsequent poststreptococcal glomerulonephritis.

  • Treatment speeds healing and avoids spread of disease.
  • Prevent with mupirocin or triple antibiotic ointment TID to sites of minor skin trauma.
  • Remove crusts; clean with gentle washing 2 to 3 times daily; and clean with antibacterial soap, chlorhexidine, or Betadine.
  • Washing of entire body may prevent recurrence at distant sites.
  • In 2005, the Infectious Diseases Society of America (IDSA) recommended topical treatment for limited lesions and oral medication when the disease is more severe/extensive (1)[A].
  • Optimal treatment is unclear due to limited quality of evidence. Treatment reduces spread of infection and enhances resolution (2)[C].
  • Penicillin and macrolide therapy is no longer recommended. Fluoroquinolones are not indicated due to resistance patterns.
  • Consult the local hospital or health department for microbial resistance information.
  • Nonbullous (minor spread, treat 7 days; widespread, treat 10 days); bullous (treat 10 days)
    • Retapamulin 1% ointment to be applied BID for 5 days
    • Mupirocin (Bactroban) 2% topical ointment applied TID for 5 to 7 days (nonbullous only); not as effective on scalp as around mouth
    • Dicloxacillin: adult 250 mg PO QID; pediatric <40 kg: 12 to 25 mg/kg/day divided q6h; >40 kg: 125 to 250 q6h
  • Dicloxacillin, cephalexin, topical mupirocin, and fusidic acid are effective unless local staphylococcal strains are resistant. (For methicillin-resistant S. aureus [MRSA] infections, treatment options include clindamycin, tetracyclines, or trimethoprimsulfamethoxazole.) Oral doses given for 7 days are usually sufficient (3)[C].
  • 1st-generation cephalosporins
    • Children
      • Cephalexin 25 to 50 mg/kg/day divided, q6-12h
      • Cefaclor 20 to 40 mg/kg/day divided q8h
      • Cephradine 25 to 50 mg/kg/day divided q6-12h
      • Cefadroxil 30 mg/kg/day divided BID
    • Adults
      • Cephalexin 250 mg up to QID
      • Cefaclor 250 mg TID
      • Cephradine 500 mg BID
      • Cefadroxil 1 g/day in divided doses
  • Clindamycin 300 mg q6-8h
  • Severe bullous disease may require IV therapy such as nafcillin or cefazolin.
If resistant or extensive infections occur, especially in immunocompromised patients
Monitor for microbial resistance patterns.
  • Athletes are restricted from contact sports.
  • School and daycare contagious restrictions
  • Children can return to school 24 hours after initiation of antimicrobial treatment.
Patient Monitoring
If not clear within 7 to 10 days, culture the lesions.
Avoidance of infection spread is the key; hand washing is vital, especially for reducing spread in children.
  • Complete resolution in 7 to 10 days with treatment
  • Antibiotic treatment will not prevent or halt glomerulonephritis, as it will rheumatic fever.
  • If not clear within 7 to 10 days, culture is necessary to find resistant organism.
  • Recurrent impetigo: Evaluate for carriage of S. aureus in nares (also perineum, axillae, toe web). Apply mupirocin ointment to nares BID for 5 days for clearance/decolonization.
1. Koning S, van der Sande R, Verhagen AP, et al. Interventions for impetigo. Cochrane Database Syst Rev. 2012;(1):CD003261.
2. Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft-tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014;59(2):147-159.
3. Del Giudice P, Hubiche P. Community-associated methicillin-resistant Staphylococcus aureus and impetigo. Br J Dermatol. 2010;162(4):905.
Additional Reading
  • George A, Rubin G. A systematic review and metaanalysis of treatments for impetigo. Br J Gen Pract. 2003;53(491):480-487.
  • Parish LC, Jorizzo JL, Breton JJ, et al. Topical retapamulin ointment (1%, wt/wt) twice daily for 5 days versus oral cephalexin twice daily for 10 days in the treatment of secondarily infected dermatitis: results of a randomized controlled trial. J Am Acad Dermatol. 2006;55(6):1003-1013.
  • Stanley JR, Amagai M. Pemphigus, bullous impetigo, and the staphylococcal scalded-skin syndrome. N Engl J Med. 2006;355(17):1800-1810.
See Also
Algorithm: Rash, Focal
  • L01.00 Impetigo, unspecified
  • L01.01 Non-bullous impetigo
  • L01.03 Bullous impetigo
Clinical Pearls
  • Superficial, intraepidermal infection
  • Predominantly staphylococcal in origin
  • Microbial resistance patterns need to be monitored.
  • Topical treatment is recommended for limited lesions and oral medication only when the disease is more severe/extensive.