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Dermatology

Impetigo

Impetigo is a contagious superficial bacterial skin infection, usually caused by Staphylococcus aureus or Streptococcus pyogenes, presenting as non-bullous crusted erosions or bullous flaccid blisters.

In a nutshell

Impetigo is a contagious superficial bacterial infection. Non-bullous disease causes honey-coloured crusts; bullous disease causes larger flaccid blisters. Diagnose clinically, reduce spread, use hydrogen peroxide 1% for suitable localised non-bullous disease, use topical or oral treatment according to extent, and use oral antibiotics for bullous, systemic or high-risk disease. Reassess non-response and recurrence.

Classic presentation

A child has small vesicles around the nose that rupture into honey-coloured crusts, with little systemic illness; a second patient has larger flaccid blisters and needs oral treatment.

Key points

  • Non-bullous impetigo produces superficial erosions with honey-coloured crusts; bullous impetigo produces larger flaccid blisters.
  • Localised non-bullous disease in a well patient: consider hydrogen peroxide 1% cream first.
  • Widespread non-bullous disease may need topical or oral treatment; bullous, systemic or high-risk disease needs oral antibiotics.
  • Do not combine topical and oral antibiotics routinely, and avoid prolonged or repeated topical antibiotic use.
  • Swab treatment-resistant or recurrent disease and consider nasal decolonisation in frequent recurrence.
  • Impetigo is highly contagious: hand hygiene, no shared towels and appropriate school or childcare exclusion are high-yield advice.
  • Think cellulitis, herpes simplex and staphylococcal scalded skin syndrome when the pattern or systemic state is wrong.

First-line investigation

Clinical diagnosis and examination of extent, bullae, systemic state and underlying skin disease; swab recurrent or treatment-resistant infection.

Management

Assess bullae, spread and systemic risk

  • Distinguish non-bullous from bullous disease, assess extent and systemic state, and urgently escalate cellulitis, sepsis, extensive exfoliation or suspected staphylococcal scalded skin syndrome.3,1

Control transmission

  • Use hand hygiene, avoid scratching and shared towels or bedding, wash contaminated items and follow current UKHSA exclusion advice for school or childcare.2,5

Choose treatment by extent and morphology

  • Use hydrogen peroxide 1% for suitable localised non-bullous disease; use a short topical or oral pathway for widespread non-bullous disease; use oral antibiotics for bullous, systemic or high-risk disease, without routine combination therapy.3,4

Swab non-response and recurrence

  • Reassess treatment failure for alternative diagnoses and complications; swab persistent or recurrent disease, consider nasal carriage and involve specialist or microbiology advice when recurrence is frequent or resistance is suspected.3,1

Treat predisposition and safety-net

  • Manage underlying eczema, scabies or skin trauma, complete prescribed treatment and advise urgent review for rapid spread, fever, increasing pain, spreading erythema, eye involvement or failure to improve.3,2

Exam traps

  • Bullous impetigo is not managed as a small localised crusted lesion; use oral treatment and consider specialist advice.
  • Do not routinely combine topical and oral antibiotics.
  • Crusted lesions can be bacterial infection, but eczema, herpes simplex, scabies and cellulitis are important alternatives.
  • A swab is particularly useful for recurrence or treatment failure, not mandatory before every first treatment.
  • Topical fusidic acid and mupirocin resistance is a stewardship issue; follow current NICE and BNF limits.
  • Do not miss staphylococcal scalded skin syndrome in an infant or a systemically unwell patient with widespread tenderness and exfoliation.

Illustrations

Severe non-bullous impetigoClinical photograph showing facial superficial erosions and yellow-brown crusted lesions in non-bullous impetigo; include a range of skin tones in the wider image campaign.James Heilman, MD, Wikimedia Commons · CC-BY-SA-3.0
Bullous impetigoClinical photograph of flaccid blisters and a scale collarette in bullous impetigo, illustrating the distinction from non-bullous crusted disease.Littlekidsdoc, Wikimedia Commons · CC-BY-SA-4.0

Key sources

  1. British Association of Dermatologists: Impetigo patient information leaflet (BAD consensus information on clinical appearance, bullous disease, diagnosis, treatment, recurrence and spread reduction; updated November 2024 and accessed 4 August 2026.)Updated 1 Nov 2024
  2. NHS: Impetigo (Current NHS information on contagiousness, hygiene, treatment, return to school or work and recurrent disease; accessed 4 August 2026.)
  3. NICE NG153: Impetigo: antimicrobial prescribing (NICE antimicrobial-prescribing recommendations for hygiene, localised and widespread non-bullous disease, bullous disease, reassessment, referral and antimicrobial choice; published 26 February 2020 and accessed 4 August 2026.)Updated 26 Feb 2020
  4. British National Formulary (BNF) (BNF online prescribing information for topical antiseptics, topical antibiotics and oral antibiotics; current product-specific dosing, age, pregnancy, renal and interaction details must be checked at the point of care; accessed 4 August 2026.)
  5. UKHSA: Public health exclusion periods in children and young people's settings (Current UKHSA public-health exclusion period for impetigo: until blisters have scabbed or 2 days after starting antibiotics; updated 9 July 2026 and accessed 4 August 2026.)Updated 9 Jul 2026

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.