The child with a rash
Rashes make juniors panic — they don't need to. Ask the right questions, learn the visual cues, and most rashes name themselves. Decide how urgent it is, rule out the dangerous ones, then let the context make the diagnosis. Built for revision, not live patient decisions.
Settle them, and sort the urgency
before the diagnosisEvery rash falls into one of three groups
act now
- Any rash with abnormal vitals or shock (tachycardia, slow CRT, low BP), whatever the rash looks like
- Any rash with airway compromise: swollen lips or tongue, stridor, wheeze → anaphylaxis
- Non-blanching rash in an unwell or febrile child
- A rash a few days after a burn or wound → toxic shock
- Skin that is painful, blistering or peeling, or sore eyes and mouth
act soon (hours)
- Palpable rashes, such as vasculitic (HSP) purpura
- Polymorphous rashes with mixed shapes and colours (pink, purple, brown), which suggest an abnormal immune reaction (e.g. erythema multiforme, Kawasaki, drug reaction)
- Non-blanching rash in a well, afebrile child (ITP, leukaemia, NAI)
primary care
- Blanching rash with normal vitals: mostly viral exanthems (over 200 viruses can cause one)
- Papular delayed-hypersensitivity rashes (insect bites, pityriasis rosea)
- Harmless in themselves; they often come to the ED for another reason
Red flags — what each should make you think
Three habits make you good at rashes. Use a good light. Carry a magnifying glass (3–5×). And always look in the mouth, even if the parents say there's nothing there. Koplik spots, ulcers and a strawberry tongue have each made a diagnosis on their own.
If they're in the "act now" group — ABCDE first, the diagnosis can wait
- AAirwayangioedema or stridor → IM adrenaline now (anaphylaxis); get anaesthetics if the airway is at risk
- BBreathingoxygen, look for wheeze
- CCirculationIV/IO access, cultures, gas and lactate, fluid bolus if shocked
- ℞Treat the likely killerpurpuric and unwell → IV ceftriaxone now; anaphylaxis → adrenaline
- ☎Seniors and PICU earlyplus dermatology, ophthalmology or surgeons as the picture dictates
Ask the right questions, then describe what you see
history + visual cuesThe focused rash history — seven questions
You don't have 40 minutes in the ED. Ask these seven every time:
- Fever? Before, during or after the rash appeared?
- Drugs? Anything in the last few weeks, especially antibiotics and anticonvulsants. Prescribed, bought or herbal.
- Travel? Abroad, camping, forests (tick bites, Lyme disease).
- Allergies or exposures? New foods, plants, chemicals, soaps, pets.
- Contacts? Anyone at home, school or nursery with a similar rash (scabies, chickenpox, measles, mpox)?
- Recent illness? Sore throat, cold or diarrhoea in the last 1–2 months. Some rashes are a delayed reaction to an earlier illness.
- Associated features? Itch, pain, joint pain, abdominal pain, lymph nodes, liver or spleen, breathing or gut symptoms.
Also check vaccination status (measles, chickenpox), and whether vulnerable contacts at home (pregnant, newborn, immunocompromised) could be exposed.
Describe the rash — the four visual cues
- 1 · Size and shape (morphology). What is each individual lesion? (See the glossary below.)
- 2 · Distribution. Localised (one area) or generalised (more than two areas). Symmetric or asymmetric. Flexor or extensor surfaces. Central (trunk) or peripheral / acral (hands, feet, face). Discrete lesions or coalescing into patches.
- 3 · Pattern. One type of lesion, or polymorphous (several types together)? Any shape: rings, target lesions, serpiginous lines, a "Christmas tree" along the skin lines of the back?
- 4 · Colour. Pink, bright red, purple, brown, golden-yellow crust, or a mixture? Does it blanch (glass test)?
Darker skin: redness can look purple, brown or grey, and is easier to miss. Check the palms, soles, conjunctivae and mouth for petechiae, and feel for texture.
Glossary — the words that make your description useful
Flat
Raised & solid
Fluid-filled
Surface changes
Combine the terms: maculopapular (flat spots plus small bumps), papulovesicular (bumps plus blisters). A good description sounds like: "A generalised, symmetric, central, blanching, pink maculopapular rash, partly coalescing."
See examples: DermNet — terminology in dermatology ↗The rashes you must not miss
tap to open eachWhat points toward it, what would rule it in, and how to manage it. Each card links to images.
A baby in the first weeks of life (usually weeks 1–2, can be up to about 6 weeks) with a few vesicles, plus vague signs: temperature instability (often low), lethargy, poor feeding, floppiness, apnoea, seizures. Ask about cold sores in parents or visitors in recent weeks. Only about half have skin lesions, and CNS disease often has none.
HSV PCR of vesicle fluid, blood and CSF; full septic screen including LP; LFTs.
Start high-dose IV aciclovir immediately, per BNFc and your neonatal guideline, alongside antibiotics; don't wait for results. Admit under the neonatal or paediatric team. Untreated, skin-only disease often progresses to disseminated or CNS disease within days, and disseminated disease is frequently fatal. Prompt aciclovir greatly improves survival and outcome.
Petechiae or purpura that don't blanch, often spreading, in a febrile or unwell child. Early on it can be a blanching macular rash, and some children never get a rash. Look for cold peripheries, leg pain and mottling.
Clinical; treat before any test. Purpura fulminans (large, spreading, dusky purpura) means advanced disease.
IV/IO ceftriaxone immediately, fluid resuscitation, senior and PICU now. Notify public health, who arrange contact prophylaxis.
Sudden urticaria or flushing after a trigger (food, drug, sting), with lip or tongue swelling, stridor, wheeze, vomiting or collapse. Skin signs are absent in some cases.
Clinical. Take mast cell tryptase samples after treatment.
IM adrenaline 1:1000 into the anterolateral thigh: under 6 months 100–150 micrograms; 6 months–6 years 150 micrograms; 6–12 years 300 micrograms; over 12 years 500 micrograms. Repeat after 5 minutes if no better. Oxygen, fluids, senior help; refractory anaphylaxis needs an adrenaline infusion. Observe, then refer to allergy and give an adrenaline auto-injector.
A flu-like prodrome, then painful dusky or target-like lesions, blisters and skin loss, with two or more mucosal sites involved (eyes, mouth, genitals). Triggers: drugs (anticonvulsants, sulfonamides, some antibiotics), or Mycoplasma in children.
Clinical, with a positive Nikolsky sign (skin shears with gentle pressure); confirmed on biopsy. Estimate the body surface area affected.
Stop the suspected drug. Treat like a burn: fluids, temperature control, pain relief, nutrition, eye care. Get dermatology and ophthalmology same day; transfer to burns or ITU for extensive skin loss.
SSSS: an infant or young child (including neonates: spots on the face, then raw peeling areas in the axillae and groin, and a sleepy baby not waking for feeds), fever, irritable, tender erythema worst in the flexures and around the mouth, then superficial blistering and peeling; mucosa spared. TSS: a burn, wound or skin infection, then fever, diffuse "sunburn" erythroderma, shock and multi-organ involvement.
Clinical. Take swabs from the likely source and blood cultures (often negative in SSSS).
IV antibiotics per local policy (anti-staphylococcal, often with clindamycin for toxin), fluids, analgesia, skin care. TSS: sepsis pathway, source control (remove packing, debride), PICU.
A child with eczema whose skin suddenly gets worse and painful, with clusters of uniform punched-out erosions or vesicles, often with fever and lethargy.
Clinical. Swab a lesion for HSV PCR, but don't wait for the result.
Start aciclovir the same day: IV if unwell, widespread or very young. Get urgent ophthalmology if lesions are around the eye. Watch for secondary bacterial infection.
Fever for 5 days or more (often high, unremitting, poorly responsive to antipyretics) with: bilateral non-exudative conjunctivitis, typically sparing the area around the iris; red cracked lips or strawberry tongue; polymorphous rash, often with perineal redness and peeling; red, swollen hands and feet, with fingertip peeling in the second week; anterior cervical lymph node. Redness at an old BCG scar is a useful clue. An extremely miserable child.
Complete Kawasaki: fever ≥5 days plus 4 of the 5 features above. Incomplete Kawasaki: fewer features, which are most common in infants, who have the highest coronary risk. Features come and go, so ask specifically about each one, even if it's absent now.
Clinical, supported by bloods: high CRP / ESR, normocytic anaemia, raised platelets in the second week, low albumin, raised ALT. Urine shows sterile pyuria. Echocardiogram.
Same-day paediatric referral. IVIG plus aspirin under specialist care, ideally within 10 days, to protect the coronary arteries.
A widespread rash 2–8 weeks after starting a drug (anticonvulsants, some antibiotics, allopurinol), with fever, facial swelling and lymphadenopathy. Much sicker than a simple drug rash.
FBC (eosinophilia, atypical lymphocytes), LFT (hepatitis), U&E (renal involvement).
Stop the drug, admit, and refer to dermatology and paediatrics; systemic steroids under specialist care. Record the drug as an allergy.
ITP: a well child, petechiae and bruising, often after a viral illness. Leukaemia: pallor, tiredness, bone pain, lymph nodes, liver or spleen. HSP (IgA vasculitis): palpable purpura on the buttocks and backs of the legs, joint pain, abdominal pain. Purpura in an unusual distribution, or an unwell child, is not HSP until proven otherwise. NAI: bruising in a non-mobile baby, unusual sites, patterns, or a story that doesn't fit.
FBC and blood film; clotting; CRP and cultures if any doubt about infection. HSP: BP and urine dip for nephritis.
If you can't confidently exclude meningococcal disease, treat for it. Abnormal film → paediatric haematology the same day. HSP: analgesia, and arrange BP and urine follow-up. Suspected NAI → follow safeguarding procedures and involve a senior.
Public health matters too
Measles is back in UK EDs as vaccination rates fall. Vaccinated children can still occasionally catch it. It is notifiable and very infectious, from shortly before the prodrome until 4 days after the rash appears. Isolate immediately, notify UKHSA, and identify vulnerable contacts. Scarlet fever, meningococcal disease and rubella are also notifiable. UKHSA — measles · images ↗
Reach a diagnosis — let the context decide
the algorithm- 1Abnormal vitals or airway?Yes → act now (stage 1). The exact diagnosis is secondary.
- 2Does it blanch?No → the non-blanching pathway: meningococcal if febrile or unwell; ITP, leukaemia, HSP or NAI if well (stage 3).
- 3Skin pain, blisters or mucosa involved?Yes → SJS/TEN, SSSS or eczema herpeticum until proven otherwise.
- 4Describe the morphologyMaculopapular? Papular? Vesicular? Sandpaper? Wheals? This picks the branch below.
- 5Add the contextFever, drugs, contacts, recent illness, itch, mouth lesions. The same-looking rash becomes a different diagnosis.
- 6Look in the mouthKoplik spots → measles. Ulcers → HFMD or herpes. Strawberry tongue → scarlet fever or Kawasaki.
Many rashes look almost the same; even a dermatologist couldn't separate them from a photo without a biopsy. What separates them is the context. Change one answer in the history (a new drug, a sibling with the same rash, ulcers in the mouth) and the diagnosis changes completely. That's why the seven questions matter.
Branch A — a central maculopapular rash on the trunk
Viral exanthem
Pityriasis rosea
Drug eruption
Branch B — a peripheral papular rash (limbs, hands, feet): same look, different story
Papular urticaria
Scabies
Gianotti–Crosti
Hand, foot & mouth
Dermatitis herpetiformis
Branch C — the other common ones you'll see on a shift
Chickenpox
Scarlet fever
Roseola
Urticaria
Impetigo
HSP (IgA vasculitis)
Branch D — the classic childhood exanthems, side by side
Measles
Rubella
Slapped cheek (parvovirus B19)
Shingles in a child
Glandular fever (EBV)
Branch E — the newborn with spots (first weeks of life)
Most newborn spots are benign and need only reassurance. Exhausted parents need a confident explanation. Two rules: vesicles in a neonate are herpes until proven otherwise, and any rash in a baby who is quiet, feeding poorly, or hot or cold is sepsis until proven otherwise.
Erythema toxicum neonatorum
Milia
Sucking blisters
Harlequin colour change
Congenital dermal melanocytosis
Investigate — most rashes need none
test with a question in mindNon-blanching rash
Purpura in a well child (HSP)
Suspected drug reaction
Swabs
Neonate with vesicles or unwell
Kawasaki
Outpatient tests
Don't over-investigate
A well child with a blanching viral exanthem, pityriasis rosea, papular urticaria or Gianotti–Crosti needs a confident diagnosis and an explanation, not a blood test. Bloods in a drug rash often just show a raised white count or eosinophils, which can worry everyone without changing the plan.
How the plan comes together
disposition · safety nethome
Blanching rash, normal vitals, confident benign diagnosis (viral exanthem, roseola, slapped cheek, pityriasis rosea, papular urticaria, Gianotti–Crosti, HFMD, urticaria, benign newborn spots).
Tell them how long it lasts (days for most viral rashes, weeks for pityriasis rosea and Gianotti–Crosti).
same-day review
Palpable or polymorphous rashes, a non-blanching rash in a well child, a suspected drug reaction with any systemic feature, or possible Kawasaki → senior or paediatric review today.
admit / resus
Non-blanching rash and unwell, anaphylaxis, SJS/TEN, SSSS, TSS, eczema herpeticum, DRESS, any neonate with vesicles or who is unwell.
Hand over: vitals, rash description, drugs given and times, specialties contacted.
Infection control & school
- Measles — isolate in the ED; off nursery or school for 4 days after the rash appears; notifiable
- Chickenpox — until all spots have crusted over
- Scarlet fever — until 24 h after starting antibiotics; notifiable
- Impetigo — until lesions crust or 48 h after antibiotics
- Scabies — can return after the first treatment
- Rubella — notifiable; keep away from pregnant women while infectious
- HFMD, slapped cheek, roseola — no exclusion needed if the child is well
- Pregnant contacts of chickenpox, slapped cheek, rubella or measles → advise them to contact their midwife or GP promptly
Safety-netting — teach the glass test
- Press a clear glass on the rash. If the spots don't fade, come straight back (999 if the child is unwell)
- Come back if the child becomes drowsy, floppy, breathless, very pale or mottled, or stops drinking
- Come back if the skin becomes painful or blisters, or the eyes or mouth become sore
- Come back if a fever lasts 5 days or more
- For drug rashes: stop the drug, and tell the GP to record the reaction
Sort the urgency, ask the seven questions, describe what you see, look in the mouth, then let the context make the diagnosis. Parents mostly want to know three things: is it dangerous, is it catching, and how long will it last? Answer all three. Nicely done getting here.
Clerking template
copy or downloadThe child with a rash — documentation structure
A structure and prompt list to help you document and think systematically. It is not a completeness check and cannot guarantee nothing is missed — use your trust's own proforma, your seniors, and your clinical judgement. Content is AI-generated and not yet fully reviewed.