EDAITUTOR
ED Reference · Paeds Rash v0.1 · illustrated Educational use only

The Child
with a Rash

A morphology-first read for the ED — does it blanch? · purpura vs petechiae · the febrile rash — and the can't-miss diagnoses hiding behind a fever.

Glass testPurpuraMeningococcal

🔴 Rash + unwell = dangerous until proven otherwise

The one question that changes everything: does it blanch? A non-blanching rash in a febrile or unwell child means you exclude meningococcal disease & sepsis first. Purpura (>2 mm, confluent) is the real red flag — not scattered petechiae. Fully undress the child, do the glass test, and get senior review for any petechiae or purpura. If the child is unwell — bloods, cultures, meningococcal PCR and IV antibiotics, now.

Morphology
  • Petechial / purpuric — non-blanching, the high-stakes bucket
  • Maculopapular — flat + raised, blanching, the viral crowd
  • Vesiculobullous — fluid-filled (chickenpox, HFMD, SJS/TEN)
  • Erythematous / urticarial — wheals, flushing, mostly benign
⚪ tipSort into a bucket first, then name the diagnosis — distribution, fever timing and prodrome matter as much as the spots.
🟢 RCH · DermNet
Glass test
  • Press a clear glass firmly over the rash
  • Fades = blanching — viral exanthems, urticaria
  • Stays visible = non-blanching — petechiae / purpura
  • Petechiae <2 mm · purpura 2 mm–1 cm, confluent
🔴 ruleNon-blanching + fever or an unwell child → treat as meningococcal until excluded. Purpura, not isolated petechiae, drives the risk.
🟢 RCH · DFTB
Well vs unwell
  • Unwell / toxic / lethargic → resus lane, treat first
  • Well, interactive, feeding → structured assessment
  • Poor perfusion, CRT >3 s, mottling = shock (BP is a late sign)
  • Limb pain & cold peripheries can precede the rash
⚪ tipClinical appearance beats the thermometer — lethargy is more concerning than the height of the fever.
🟢 RCH · DFTB
If unwell — act now
  • Fully undress — examine all skin + mucosa (mouth, eyes, genitals)
  • Bloods: VBG, FBC, U&E, CRP, coagulation
  • Blood culture + EDTA tubes for meningococcal PCR
  • IV access — IM or IO if difficult; don't delay the dose
🟢 doseCeftriaxone 100 mg/kg (max 4 g) IV. Give as soon as invasive infection is suspected.
🟢 RCH · CHQ
The four morphologies — tap any image to enlarge
Non-blanching petechial and purpuric rash on a child's skin

1Petechial / purpuric

Pinpoint to confluent, non-blanching lesions. The high-stakes bucket — think meningococcal, HSP, ITP.

Tap to enlarge
Clinical image · educational reference
Blanching maculopapular viral-type rash on a child

2Maculopapular

Flat macules + raised papules, blanching. The viral crowd — and the classic drug-versus-viral trap.

Tap to enlarge
Clinical image · educational reference
Fluid-filled vesicular rash on a child's skin

3Vesiculobullous

Fluid-filled vesicles or bullae — chickenpox and HFMD, but also SJS/TEN when skin is painful.

Tap to enlarge
Clinical image · educational reference
Raised urticarial wheals on a child's skin

4Erythematous / urticarial

Migrating, blanching wheals that itch — the single most common rash reason for an ED visit.

Tap to enlarge
Clinical image · educational reference
⚪ sort, then nameGet the morphology and the child's appearance first; the named diagnosis follows. Images are external educational references, not produced by ED AI Tutor.
The non-blanching lane — exclude the life-threats first
Comparison of pinpoint petechiae versus larger confluent purpura, with the tumbler test demonstrated

◆Petechiae vs purpura + the tumbler test

Purpura (larger, confluent, >2 mm) carries far more risk than scattered petechiae — and the glass/tumbler test tells them apart from a blanching viral rash.

Tap to enlarge
Clinical image · educational reference

Meningococcal disease

Don't miss

Fever + petechiae/purpura, poor perfusion, altered conscious state. The rash is absent early in up to half of cases — its absence never reassures.

Treat first, investigate later

Henoch–Schönlein purpura

IgA vasculitis

Palpable purpura, lower-limb / buttock predominant, in a well child + abdominal pain, arthritis or renal signs.

Check BP + urinalysis

ITP & haematological

Well, afebrile

Widespread petechiae, bruising, mucosal bleeding without fever suggests thrombocytopenia.

FBC + film before reassuring

Non-accidental injury

Always exclude

Unexplained bruising or petechiae in a non-mobile infant, or a history that doesn't fit.

Safeguard + senior review

Mechanical petechiae

Benign mimic

Petechiae above the nipple line after coughing, vomiting or crying, in a well, afebrile child.

Reassuring distribution

The PiC study

What changed

Post men-B/C vaccine, invasive disease in fever + non-blanching rash fell from ~10–20% to ~1%. Meningococcal PCR stays positive for days after antibiotics.

Purpura > petechiae
⚪ modern messageIn a well, vaccinated child, isolated petechiae is no longer an automatic red flag — but purpura, an unwell child, or an evolving rash always is.
Febrile rashes that blanch — but still bite

Kawasaki disease

Time-critical

Fever ≥5 days + ≥4 of: conjunctivitis, lip/oral changes, rash, extremity changes, cervical node >15 mm. Coronary risk if missed.

SJS / TEN

Derm emergency

Target lesions, dusky/blistering centres, mucosal involvement and skin pain. Usually drug-induced — stop the drug, escalate.

Toxic shock syndrome

Toxin-mediated

Diffuse "sunburn" erythroderma + fever + shock, later desquamation. Hunt the source.

Rickettsial / spotted fever

Exposure history

Fever, headache, rash to wrists/ankles/palms/soles that may turn petechial. Ask about ticks and travel.

Necrotising fasciitis

Pain out of proportion

Erythema with pain out of proportion, rapid spread, toxicity. Skin signs lag — trust the pain.

Measles

Re-emerging

Coryza, cough, conjunctivitis, Koplik spots ~2 days pre-rash; morbilliform rash spreads hairline downward. Ask immunisation status; isolate.

⚪ when in doubtIf the child looks more unwell than the rash suggests, keep these on the differential and get senior review.
The benign exanthems — tap any image to enlarge
Slapped-cheek appearance of erythema infectiosum (fifth disease) on a child

1Slapped cheek

Erythema infectiosum (parvovirus B19) — viral prodrome, then bright cheeks and a lacy rash on the limbs.

Tap to enlarge
Clinical image · educational reference
Sandpaper rash of scarlet fever on a child's trunk

2Scarlet fever

Group A Strep — sandpaper texture, spares palms/soles, Pastia lines in the creases, strawberry tongue.

Tap to enlarge
Clinical image · educational reference
Roseola rash appearing after fever in an infant

3Roseola

HHV-6/7 — high fever first, then a rose-pink rash appears as the fever breaks in a well-looking child.

Tap to enlarge
Clinical image · educational reference
Chickenpox vesicles in different stages on a child's skin

4Chickenpox

VZV — crops of lesions in different stages (macule → vesicle → crust). Incubation 10–21 days.

Tap to enlarge
Clinical image · educational reference

Measles

Measles virus

Coryza, cough, conjunctivitis, Koplik spots; rash spreads hairline downward.

Rubella

Rubella virus

Mild pink rash with tender suboccipital / postauricular nodes.

Hand, foot & mouth

Coxsackie / entero

Oral ulcers + vesicles on hands, feet and around the mouth.

Pityriasis rosea

HHV-6/7 assoc.

Herald patch, then a symmetric "Christmas-tree" pattern on the trunk.

Urticaria

Viral / allergic

Migrating, blanching wheals that itch; individual lesions last <24h.

Scarlet fever

Group A Strep

Sandpaper rash, spares palms/soles, Pastia lines, strawberry tongue.

Viral vs drug
  • In a child, a morbilliform rash is more likely viral; in an adult, more likely drug
  • EBV, HHV-6 and CMV can cause the rash directly or interact with a concurrent drug
  • The acute phase often can't be reliably distinguished
  • Avoid stamping "penicillin allergy" on a single viral-context rash — document and reassess
🔴 escalateSkin pain, mucosal involvement, facial oedema, blistering or systemic upset → think SJS/TEN or DRESS, not a simple exanthem.
🟢 DermNet · DFTB
Assessing across skin tones
  • Erythema can look violaceous, brown or grey — not red — in darker skin
  • Palpate, don't just look — warmth, induration and texture carry information
  • Check palms, soles, conjunctivae and oral mucosa; use good lighting
  • For non-blanching rashes, lean on the glass test and the whole picture
⚪ resourceDFTB Skin Deep is a free, open-access image library across the full range of skin tones — a counterweight to single-tone atlases.
🟢 DFTB Skin Deep
Red flags — escalate now
  • Non-blanch + feverPetechial or purpuric rash with fever or an unwell child → exclude meningococcal / sepsis.
  • Shock / sepsisPoor perfusion, tachycardia, mottling, altered conscious state.
  • Pain out of proportionErythema with pain beyond the visible findings → necrotising fasciitis.
  • Mucosal + target/bullaeEye, mouth or genital involvement with blistering → SJS/TEN.
  • Rapidly evolvingA rash spreading or changing in front of you.
  • Ill child, minor rashSystemic illness that outweighs the rash — trust the child, not the spots.
  • Newborn petechiaeAny petechiae in a neonate → prompt senior review.
🟢 RCH · DFTB · CHQ

ED AI Tutor — ED Reference Series · v0.1 · For clinician education only. Not a substitute for clinical judgement, local guidelines or senior oversight. Any child with a rash must be assessed in the context of the full clinical picture.