AKT · Dermatology/Infections & infestations

Impetigo

Staphylococcus aureus (± Streptococcus pyogenes)

Overview

A superficial, highly contagious bacterial skin infection, usually Staphylococcus aureus. Non-bullous (the common form) shows golden honey-coloured crusts around the mouth/nose; bullous impetigo (toxin-mediated) shows flaccid blisters. Common in children.

Recognise

Non-bullous: thin-walled vesicles/pustules that rupture to leave the classic golden/honey-coloured crust, typically perioral/perinasal
Bullous: flaccid fluid-filled blisters (exfoliative toxin) that rupture leaving a collarette of scale
Very contagious — spreads by direct contact and fomites; mild itch, well child

Red flags

Widespread bullous impetigo in a neonate/infant → consider staphylococcal scalded skin syndrome; systemic illness

Differentials & how to tell them apart

Herpes simplexgrouped vesicles on an erythematous base, recurrent at the same site, painful/tingling

Eczema herpeticummonomorphic punched-out erosions on eczema, unwell — HSV emergency

Staphylococcal scalded skin syndromewidespread superficial peeling, Nikolsky positive, unwell child

Tinea/contact dermatitisscaly annular or eczematous, no honey crust

Clinical image

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Impetigo — clinical imagesDermNet

Investigations

Clinical diagnosis. Swab for culture if recurrent, widespread, bullous, or not responding (and to check for MRSA).

Management

Localised non-bullous, well person → hydrogen peroxide 1% cream first-line

1Localised non-bullous impetigo in a well person → topical hydrogen peroxide 1% cream; if unsuitable/ineffective → a short course of topical fusidic acid.Gate: Escalate to ORAL antibiotics (flucloxacillin) when impetigo is widespread, BULLOUS, or the person is systemically unwell — topical therapy is only for localised non-bullous disease
2Widespread/bullous/systemically unwell → oral flucloxacillin (clarithromycin or erythromycin if penicillin-allergic / in pregnancy).
3Hygiene advice (no sharing towels, stay off school/work until lesions are crusted/healed or 48h of antibiotics); swab + microbiology advice if recurrent or MRSA suspected.

Hydrogen peroxide 1% cream — first-line for localised non-bullous impetigo in a well person (NICE 2020)

Topical fusidic acid — localised disease if hydrogen peroxide unsuitable/ineffective

Oral flucloxacillin — widespread, bullous, or systemically unwell (clarithromycin/erythromycin if penicillin-allergic)

Key points

A post-streptococcal complication is glomerulonephritis. Exclusion from school until lesions are crusted or 48 hours after starting antibiotics. Recurrent impetigo → consider nasal Staph carriage.

Monitor & prognosis

Resolution; recurrence prompts a carriage/MRSA check.

Heals without scarring; very responsive to treatment.

Source: NICE NG153 (impetigo); NICE CKS Impetigo