Impetigo

impetigo · school sores · bullous impetigo · impetiginised eczema

A superficial bacterial skin infection with a golden crust - the question worth asking is what it is growing on.

GPBand B

Red flags

Systemic upset, fever or spreading erythema - cellulitis or deeper infection rather than impetigo
Widespread bullous disease in an infant with skin tenderness - reconsider staphylococcal scalded skin syndrome
Recurrent impetigo - look for an untreated underlying dermatosis or a colonised contact
Failure to respond to appropriate treatment
Peri-orbital involvement, or infection in an immunosuppressed patient

Recognise

On light skin

Thin-walled vesicles or pustules that rupture to leave the characteristic golden-yellow honey-coloured crust on a red base; bullous forms show flaccid blisters leaving a collarette of scale.

On brown and black skin

The surrounding erythema is often invisible, but the golden-yellow crust itself is a colour of exudate, not of skin, and looks the same on every skin tone - so this is one of the few classic signs that transfers intact. The greater risk in brown and black skin is the opposite one: underlying eczema is frequently lichenified, follicular or hyperpigmented rather than red, so impetiginised eczema is under-recognised and treated as simple impetigo when the eczema also needs treating. Examine the surrounding skin texture. Healing leaves marked post-inflammatory pigment change, not scarring.

In any skin tone

Golden or honey-coloured crust - the defining sign
Superficial, non-tender to mildly tender, and the patient is systemically well
Spreads by scratching and autoinoculation, and between close contacts
Bullous form: flaccid blisters that rupture easily, commoner in infants
Ask what it is growing on - eczema, scabies, head lice or chickenpox underneath changes the treatment

Distribution

Most often around the mouth and nose and on exposed skin of the face and limbs. Bullous impetigo favours the trunk, flexures and nappy area, and is commoner in infants.

Photographs

Impetiginised eczema around the mouth. The golden-yellow crust is the sign, and it reads the same on black skin as on white - colour is doin — Impetiginised eczema around the mouth. **The golden-yellow crust is the sign, and it reads the same on black skin as on white** - colour is doing the work here, but it is the colour of the crust, not of the skin underneath. Note how little surrounding redness there is: on skin this dark the inflammation is invisible, so judging severity by how angry it looks will underestimate it.
Fitzpatrick IV-VI (Fitzpatrick type estimated from the photograph, not stated by the source) · Oladokun RE, Lehloenya RJ, Hlela C, Ubesie AC, Katibi SO, Malande OO, Eley BS · Atlas of Paediatric HIV Infection, UCT Libraries Press 2018 - Chapter 1: Bacterial Infections, p5 · CC BY 4.0

Bullous impetigo in an infant. The bullae have ruptured and left shallow raw erosions ringed by a collarette of loose scale - the remains of — Bullous impetigo in an infant. The bullae have ruptured and left **shallow raw erosions ringed by a collarette of loose scale** - the remains of the blister roof. Widespread bullous impetigo in a baby is the lesion that gets confused with staphylococcal scalded skin syndrome; the discriminator is that these are discrete lesions with normal skin between them.
Fitzpatrick IV-VI (Fitzpatrick type estimated from the photograph, not stated by the source) · Oladokun RE, Lehloenya RJ, Hlela C, Ubesie AC, Katibi SO, Malande OO, Eley BS · Atlas of Paediatric HIV Infection, UCT Libraries Press 2018 - Chapter 1: Bacterial Infections, p4 · CC BY 4.0

Provenance for every photograph in this library: image licences. How much of the corpus still has no darker-skin photograph: skin tone coverage.

Mimics

Staphylococcal scalded skin syndrome — Bullous impetigo and SSSS are caused by the same toxins; SSSS is generalised, the child is febrile and miserable, and the skin shears
Eczema herpeticum — Crusted lesions on eczema may be herpes simplex rather than bacteria - look for monomorphic punched-out erosions and treat urgently if in doubt
Atopic eczema and infected eczema — Impetiginised eczema is both diagnoses at once; treating only the infection leaves the cause
Hand, foot and mouth disease — Perioral lesions can look similar early on

What to do in the ED

Treat per NICE NG153 and local policy. 1.1.2: hydrogen peroxide 1% cream first-line for localised non-bullous impetigo in someone who is not systemically unwell or at high risk of complications. 1.1.3: a short course of a topical antibiotic only if hydrogen peroxide 1% cream is unsuitable. Widespread or bullous disease, or a patient who is systemically unwell or at high risk of complications, takes an antibiotic. 1.1.10: if it worsens or fails to improve on hydrogen peroxide, step to a topical antibiotic while localised, or a topical or oral antibiotic once widespread
Examine and treat the underlying skin condition, not just the infection - most commonly eczema
Consider and exclude eczema herpeticum in any child with eczema and crusted lesions; if in real doubt, start aciclovir as well
Swab if it is recurrent, extensive, or has failed treatment
Advise on hygiene: separate towels and flannels, hand washing, avoid scratching, cover lesions where practical
Advise exclusion from school or nursery until all blisters have formed scabs, or 2 days after starting antibiotics (UKHSA wording). CKS words the same rule as 48 hours after commencing treatment, hydrogen peroxide cream or antibiotics - use that, so first-line treatment does not cost the child extra days off

Disposition

Treat and discharge. Admit only for systemic illness, extensive bullous disease in an infant, or when staphylococcal scalded skin syndrome is a possibility.

Safety-netting

Keep away from school or nursery until all the sores have scabbed over, or for 2 days after starting treatment - CKS runs that clock from either the hydrogen peroxide cream or an antibiotic, so a child on hydrogen peroxide is not kept off for longer. Use separate towels and flannels. Return if the sores spread despite treatment, if the skin around them becomes red, hot, swollen or painful, if the child develops a fever or becomes unwell, or if large areas of skin start to peel or become tender to touch.

Sources

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