Impetigo
Impetigo is a superficial, highly contagious bacterial skin infection most commonly caused by Staphylococcus aureus and/or Streptococcus pyogenes. It typically occurs where the epidermal barrier is broken (eczema, insect bites, trauma) and is most common in young children.
Two clinical forms are recognised: non‑bullous (the common “honey‑coloured crust” lesions) and bullous (toxin‑mediated blisters).
Management in the emergency department centres on accurate diagnosis, targeted therapy guided by disease extent and antimicrobial stewardship, infection‑control advice, and recognition of complications or need for specialist input (NICE NG153).
Clinical features
- Non‑bullous (typical) impetigo: vesicles or pustules that rupture to form golden or honey‑coloured crusts on an erythematous base. Lesions are often perioral or perinasal, may be multiple and pruritic, and systemic symptoms are uncommon.
- Bullous impetigo: caused by S. aureus strains producing exfoliative toxins that cleave desmoglein‑1, producing flaccid bullae which rupture to leave thin varnish‑like erosions. More common in infants and may be more extensive.
- Transmission: direct contact with lesions or indirect via fomites (towels, clothing). High transmissibility in households and childcare settings.
Differential diagnosis (key points)
- Herpes simplex: grouped painful vesicles, often tender and localised; may have prodrome and systemic symptoms.
- Eczema with secondary infection: look for background atopic dermatitis distribution and history.
- Contact dermatitis.
- Scabies: typically causes intense itch and characteristic burrows.