About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
The Bottom Line
- Non-bullous (~70%): thin-walled vesicles rupture to golden/honey-coloured crusts around nose/mouth
- Bullous (~30%): large flaccid bullae from S. aureus exfoliative toxin — more common in neonates
- Highly contagious — exclude from school until crusted or 48 hours after antibiotics
- Localised: topical hydrogen peroxide 1% cream first-line (reduces resistance) or fusidic acid
- Extensive: oral flucloxacillin 500 mg QDS for 5-7 days
Overview
Impetigo is a highly contagious superficial bacterial infection. Non-bullous (~70%) is caused by S. aureus/GAS producing golden/honey-coloured crusts. Bullous (~30%) is caused by S. aureus exfoliative toxins causing intra-epidermal cleavage. Can be primary or secondary (impetiginisation of pre-existing eczema/scabies).
Epidemiology
Commonest bacterial skin infection in children — peak age 2-5 years. Spread by direct contact and autoinoculation. More common in warm weather. Risk factors: pre-existing skin disease, minor trauma, overcrowding.
Clinical Features
Symptoms
Non-bullous: golden/honey-coloured crusted lesions around nose and mouth
Bullous: large flaccid blisters with clear/yellow fluid
Mild discomfort — systemically well in most cases
Fever, spreading cellulitis
Signs
Golden/honey crusts on erythematous base — pathognomonic
Thin-roofed flaccid bullae (bullous form)
Regional lymphadenopathy
Investigations
First-line
Clinical diagnosisGolden crusts around nose/mouth in a child is classic
Second-line
Skin swab MC&SIf recurrent or not responding — identify MRSA
1
General
- Hand hygiene, avoid touching lesions
- Exclude from school until crusted or 48h after antibiotics
- Remove crusts gently with warm water
2
Localised
- First-line: topical hydrogen peroxide 1% cream BD-TDS for 5 days
- If ineffective: topical fusidic acid 2% TDS for 5 days
3
Extensive/bullous/systemically unwell
- Oral flucloxacillin 500 mg QDS for 5-7 days
- Pen allergy: clarithromycin 500 mg BD
Complications
- Post-streptococcal glomerulonephritis: 1-3 weeks after GAS impetigo
- SSSS: In neonates from S. aureus exfoliative toxin
UKMLA Exam Tips
- 1Golden/honey crusts around nose/mouth in child = impetigo
- 2Bullous impetigo: S. aureus exfoliative toxin — intra-epidermal splitting
- 3NICE recommends hydrogen peroxide 1% as first-line topical (reduce resistance)
- 4Post-streptococcal GN can follow impetigo (but NOT rheumatic fever — RF only follows pharyngitis)
- 5SSSS splits superficially (intra-epidermal); TEN at dermo-epidermal junction
practicetest your knowledge on impetigoApply what you've learnt with UKMLA-style questions from the iatroX Q-Bank — dermatology and beyond.
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