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InfectionCommonICD-10 L01.x

Impetigo

Impetigo contagiosa · non-bullous impetigo · bullous impetigo · ecthyma (deep / ulcerative)

Impetigo is a superficial bacterial skin infection — the commonest paediatric skin infection in the UK and a frequent adult eruption. It is classified as non-bullous (~70%, mostly Staphylococcus aureus + Streptococcus pyogenes) or bullous (S. aureus exfoliative toxin-mediated). Ecthyma is the deeper ulcerative variant. NICE NG153 (2020) underpins UK antimicrobial stewardship, recommending hydrogen peroxide 1% cream as first-line topical for localised non-bullous disease.

CurrentLast reviewed 16 May 2026
Clinical image of Impetigo
Impetigo. Image sourced from DermNet New Zealand. Used under CC BY-NC-ND 4.0. No endorsement implied.

Microbiology

  • Non-bullous (~70%): mixed Staphylococcus aureus + Streptococcus pyogenes (group A).
  • Bullous (~30%): Staphylococcus aureus producing exfoliative toxin (ET-A, ET-B) → epidermal split at desmoglein-1.
  • Ecthyma: deeper, ulcerative; usually S. pyogenes; immunosuppressed / diabetic / lower extremities.
  • MRSA increasing in community / hospital UK outbreaks.

Clinical features

  • Non-bullous impetigo:
    • Vesicles / pustules rupture to leave classic golden honey-coloured crust.
    • Face (peri-oral, peri-nasal), arms, legs.
    • Children predominantly.
    • Highly contagious — outbreaks in schools / nurseries.
  • Bullous impetigo:
    • Flaccid clear or cloudy bullae >1 cm on trunk, axillae, neck.
    • Rupture leaves collarette of scale, varnish-like residual area.
    • Infants and immunosuppressed predominantly.
    • Toxin-mediated localised SSSS variant.
  • Ecthyma:
    • Punched-out ulcer with adherent crust; lower legs commonly.
    • Deeper than impetigo — full-thickness epidermis + papillary dermis.
    • Heals with scarring.
  • Complications: post-streptococcal glomerulonephritis (rare; non-rheumatogenic), cellulitis, lymphangitis, SSSS, sepsis.

Differentials

  • Herpes simplex — grouped vesicles on erythematous base; recurrent at same site.
  • Bullous pemphigoid — autoimmune; elderly; tense bullae; DIF positive.
  • Pemphigus — flaccid bullae; mucosal-first; Nikolsky+.
  • Eczema herpeticum — disseminated HSV on disrupted skin.
  • SJS / TEN — full-thickness; drug history.
  • SSSS — generalised toxin-mediated.
  • Tinea, scabies, contact dermatitis with secondary impetiginisation.
  • Insect bite reactions.

Investigations

  • Clinical diagnosis usually adequate.
  • Bacterial swab from intact pustule / blister or from crusted lesion:
    • Local culture & sensitivity guides therapy.
    • MRSA screening if outbreak or recurrent.
  • Nasal swab if recurrent (S. aureus carrier state).
  • Bloods only if systemic features or sepsis (FBC, CRP, U&E).
  • Consider HSV PCR if grouped vesicles / unclear clinical picture.

Management (NICE NG153, 2020)

  • Localised non-bullous in children >1 year and adults (first-line):
    • Hydrogen peroxide 1% cream (Crystacide) 2-3× daily for 5 days — UK first-line, antibiotic-sparing.
  • Localised disease if hydrogen peroxide inappropriate / unsuccessful:
    • Topical fusidic acid 2% TDS for 5-7 days.
    • Topical mupirocin 2% TDS for 5-7 days (reserve for MRSA / fusidic-acid resistance).
  • Widespread / severe / bullous / ecthyma:
    • Oral flucloxacillin 500 mg QDS for 5-7 days (child: 12.5-25 mg/kg QDS).
    • Penicillin-allergic: clarithromycin 250-500 mg BD or erythromycin.
    • MRSA: doxycycline / co-trimoxazole / clindamycin per culture.
  • General:
    • Hand-hygiene, separate towels / flannels.
    • Children should stay off school until crusts dry / 48 h post-antibiotic.
    • Treat household contacts if symptomatic.
    • Decolonisation regimen for recurrent disease: nasal mupirocin + chlorhexidine body wash.

References

  1. NICE NG153. Impetigo: antimicrobial prescribing. London: NICE; 2020.
  2. Hartman-Adams H, Banvard C, Juckett G. Impetigo: diagnosis and treatment. Am Fam Physician. 2014;90:229-235.
  3. Koning S et al. Interventions for impetigo. Cochrane Database Syst Rev. 2012;1:CD003261.
  4. NHS Right Decision Service. Impetigo treatment summary. London: NHS; 2024.

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