• Clinical science



Impetigo is an infectious, predominantly pediatric skin disease caused by the bacteria Staphylococcus aureus or, less commonly, Streptococcus pyogenes (group A Streptococcus, GAS). There are both bullous and nonbullous variants. The disease causes honey-colored, crusted lesions with surrounding erythema and typically affects the face, but may also manifest on the extremities. While the diagnosis is usually made based on clinical findings, it can be confirmed with a bacterial culture. The first-line treatment for mild impetigo is a topical antibiotic (mupirocin), which typically resolves the infection without complications. An additional systemic antibiotic may be indicated in more severe cases.


  • Age: primarily affects children (especially between 2–6 years of age)
  • Prevalence: high in developing countries and underprivileged populations
  • Impetigo is highly contagious and can cause epidemics in preschools or schools.

Impetigo is the most common bacterial skin infection among children!


Epidemiological data refers to the US, unless otherwise specified.



Clinical features

  • Nonbullous impetigo (∼ 70% of cases)
    • Localization
      • Face (most common), especially around the nose and mouth
      • Extremities
    • May be pruritic but is rarely painful
    • Regional lymphadenopathy
  • Bullous impetigo (∼ 30% of cases)
    • Lesions
      • Vesicles that grow to form large, flaccid bullae, which go on to rupture and form thin, brown crusts
      • Lateral traction causes sloughing of the skin (positive Nikolsky sign)
    • Localization: trunk and upper extremities
  • Ecthyma: ulcerative impetigo that extends into the dermis; (coin-sized, superficial ulcer, with a 'punched-out' appearance)
  • Systemic signs: possible in severe cases (e.g., fever, malaise, weakness)

Impetigo should be suspected in children presenting with honey-colored crusts around the mouth and nose!



  • Generally diagnosed based on clinical presentation
  • Microbiological culture → detection of causative pathogen
    • Indications: inconclusive diagnosis, recurrence despite treatment


Differential diagnoses


The differential diagnoses listed here are not exhaustive.





We list the most important complications. The selection is not exhaustive.


  • Advise patients and caregivers to wash hands regularly.
  • To prevent the spread of the disease, children should receive antibiotic treatment for at least 24 hours before returning to daycare or school.