Is It Impetigo?
Golden crusts that spread, versus cold sores, infected eczema, ringworm, chickenpox and scabies — and the cases where it is both.
Part of the Complete Impetigo Guide.
Key fact: The giveaway is the golden-brown crust — honey-coloured, stuck on, and spreading outwards from where it started. Most things mistaken for impetigo do not crust like that, and most things impetigo is mistaken for do not spread to other people.
The impetigo pattern
- Starts as a red sore or small blister that bursts within a day or so
- Dries into a golden-brown crust that sits on the surface and looks stuck on
- Spreads outwards and to new patches, particularly where it has been touched
- Around the nose and mouth most often, and on hands and limbs
- Itchy rather than painful, usually
- Other people catch it — siblings, classmates, household members
- The person is otherwise well, in uncomplicated cases
Two features do most of the work: the honey-coloured crust, and the fact that it spreads to other people. Neither is true of the conditions below.
Cold sores
Herpes simplex around the mouth is the commonest confusion, because both crust and both sit in the same place.
| Cold sore | Impetigo |
|---|---|
| Tingling or burning a day before anything appears | No warning |
| A cluster of small blisters in one spot, usually at the lip border | Sores that spread and multiply beyond the lip |
| Crust is darker, more brown or red | Crust is golden or honey-coloured |
| Recurs in the same place | Appears wherever contact happened |
| Painful or burning | More often itchy |
They also overlap: impetigo frequently develops on top of a cold sore, because the broken skin lets bacteria in.
Infected eczema
Eczema that becomes weepy, crusted and rapidly worse is often infected — usually with the same staph that causes impetigo. The distinction matters less than it seems, because both need treating.
- Eczema first, then change — a known eczematous area that suddenly weeps, crusts, or stops responding to its usual treatment
- Golden crusting or pus on eczematous skin points to bacterial infection
- Small punched-out ulcers with fever point instead to eczema herpeticum, a herpes infection of eczematous skin. That is a same-day problem
- Treating the eczema matters too — controlling it removes the broken skin that let the infection in. See eczema and dermatitis
Widespread painful clustered blisters or punched-out sores on eczematous skin, with fever or a child who is unwell, needs urgent same-day assessment. Eczema herpeticum spreads quickly and is treated with antivirals, not antibiotics.
Ringworm
A fungal skin infection, and a different shape entirely: an expanding ring with a raised, scaly edge and a clearer centre. It is scaly rather than crusted, and it does not produce the honey-coloured surface crust.
It is contagious, but it responds to antifungal cream and not to antibiotics — so getting the label right changes the treatment. The fungal infection pages cover it.
Chickenpox and hand, foot and mouth
- Chickenpox — crops of spots appearing over several days across the whole body, at different stages at once, with fever and a generally unwell child. Impetigo does not arrive everywhere at once and does not usually come with fever
- Hand, foot and mouth disease — small blisters on palms, soles and inside the mouth, with sore throat and fever, in a pattern impetigo does not follow
- Both are viral, so neither responds to antibiotics
- Chickenpox spots can become impetiginised from scratching — a spot that becomes golden-crusted and spreads is bacterial infection on top
Scabies and insect bites
Both cause intense itching and both lead to scratched, broken skin that then becomes infected — so impetigo on top of either is common.
- Scabies — itching much worse at night, between the fingers, at the wrists, around the waist and in the armpits, often affecting several people in a household at once. It needs its own treatment, and treating only the impetigo leaves the cause in place
- Insect bites — discrete, often in a line or cluster, appearing overnight, without spreading crusts
The less common look-alikes
- Contact dermatitis — a defined area matching whatever touched it, itchy and red rather than crusted, and not contagious
- Molluscum contagiosum — small firm pearly bumps with a dimple, in children; contagious, but not crusted and self-limiting
- Shingles — painful blisters in a band on one side of the body, not crossing the midline, usually with pain before the rash
- Seborrhoeic dermatitis — greasy yellow scale on the scalp, eyebrows and nasal folds, chronic rather than spreading
- Burns and scalds in a child with unexplained blistering, where the picture does not fit an infection
When it is both
Secondary impetigo — bacterial infection on top of something else — is common enough that "is it impetigo or eczema?" is often answered with "both". The practical consequence is that treating the infection alone tends to work briefly and then fail, because the broken skin that let it in is still there.
So where impetigo appears on eczema, after scabies, on a cold sore or on scratched bites, the underlying problem needs treating at the same time.
What to do
- Look at the crust — golden and stuck on, versus scaly, greasy or dark
- Look at the spread — outwards and to new sites, and to other people
- Check whether the person is well — fever and feeling unwell point away from simple localised impetigo
- Check for something underneath — eczema, bites, a cold sore, night-time itching
- Start treatment promptly once it looks like impetigo — it shortens the contagious period from up to three weeks to 48 hours. See treatments compared
Frequently Asked Questions
How do I know if it is impetigo or a cold sore?
A cold sore usually gives a day of tingling or burning before it appears, stays as a cluster in one spot at the lip border, recurs in the same place and is painful. Impetigo arrives without warning, spreads to new patches beyond the lip, forms a golden or honey-coloured crust, and is more often itchy than painful.
Can eczema look like impetigo?
Yes, and the two frequently occur together. Eczema that suddenly weeps, crusts golden or stops responding to its usual treatment is often infected with the same bacteria that cause impetigo. Both need treating, because controlling the eczema removes the broken skin that let the infection in.
Is impetigo the same as ringworm?
No. Ringworm is a fungal infection that forms an expanding ring with a raised scaly edge and a clearer centre. It is scaly rather than crusted and responds to antifungal cream, not antibiotics. Impetigo is bacterial and forms golden-brown crusts.
My child has chickenpox and some spots have gone crusty and yellow. What is that?
That is likely to be impetigo developing on scratched chickenpox spots, which is common. Spots that become golden-crusted, spread outwards or ooze are bacterial infection on top of the viral rash and need treating in their own right.
What should I do if there is something underneath the impetigo?
Treat both. Impetigo on eczema, on scratched insect bites, on a cold sore or after scabies will usually clear briefly and then return if only the infection is treated, because the broken skin that allowed it in is still there.
References
- National Institute for Health and Care Excellence. Impetigo: antimicrobial prescribing (NG153). nice.org.uk
- NHS. Impetigo. nhs.uk
- National Institute for Health and Care Excellence. Clinical Knowledge Summary: Impetigo. cks.nice.org.uk
- UK Health Security Agency. Health protection in children and young people settings, including education. gov.uk
- NHS. Cellulitis. nhs.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Impetigo is highly contagious, and a spreading rash with fever or a child who is unwell needs assessment rather than a cream. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.