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OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Childhood viral exanthems

Dermatology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Non-blanching or systemically dangerous rash

A child with fever plus non-blanching petechiae or purpura, shock, reduced consciousness, neck stiffness, seizures, respiratory compromise, severe focal pain, extensive blistering or mucosal loss may have meningococcal sepsis, another invasive infection, encephalitis or a severe cutaneous adverse reaction.

Action: Use an ABCDE assessment, treat suspected sepsis or meningococcal disease immediately according to age-specific guidance, isolate appropriately and transfer urgently; investigations and the search for a named exanthem must not delay antibiotics, resuscitation or airway and skin-failure care.

Overview

Use timing, distribution and associated features to distinguish common childhood viral eruptions, identify sepsis and inflammatory mimics, choose targeted testing, and apply notification, isolation and high-risk-contact actions.

An exanthem is a widespread eruption accompanying systemic illness, not a diagnosis. Start with age, immunisation, prodrome, fever trajectory, contact and travel history, medicine timing, pregnancy and immunocompromised contacts. Record where lesions began, how they spread and whether they blanch. Examine mouth, conjunctiva, scalp, palms, soles and buttocks and assess hydration, breathing, circulation and neurological state. Arrange a separate waiting area and use appropriate personal protective equipment when measles or varicella is plausible; tell the receiving service before the child arrives.

Classic patterns remain useful. Measles adds the three Cs—cough, coryza and conjunctivitis—with Koplik spots and a head-to-trunk spread. Rubella tends to be milder with posterior nodes. Parvovirus gives slapped-cheek change followed by reticulate limbs and trunk. Roseola reverses the usual anxiety: high fever improves before the rash appears. Hand, foot and mouth disease targets oral mucosa and acral sites. Varicella produces pruritic vesicles in crops. Yet vaccination, partial immunity, skin tone, age and immune status modify every pattern, so epidemiology and targeted virology often matter.

Practice

Two practice questions

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DermatologyOriginal SBA

A possible measles case before arrival

An unimmunised 7-year-old has fever, cough, coryza, conjunctivitis and a rash spreading from the hairline. A parent phones asking whether to attend the surgery waiting room. What is the best immediate response?

Choose one answer, then submit
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Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • NHS measlesClinical recognition, advance contact, infectious period, complications and urgent advice.
  • UKHSA health protection in education and childcareCurrent exclusion, notification and public-health management across childhood infections.
  • NHS chickenpoxVaricella morphology, supportive treatment, medicine cautions and high-risk-contact advice.
  • NHS hand, foot and mouth diseaseAcral and oral recognition, hydration-focused care and advice on attendance and transmission.
  • NICE fever in under 5sPhysiological risk assessment, non-blanching rash, sepsis escalation and safety-netting.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom

Safety management has three layers: recognise physiological danger, prevent transmission and protect vulnerable contacts. A glass test can demonstrate non-blanching but cannot exclude sepsis when lesions blanch or have not yet appeared. Severe pain, mucosal erosions and targetoid lesions may signal Stevens–Johnson syndrome rather than infection. Five days of fever with conjunctival injection, oral change, extremity change, lymphadenopathy or rash raises Kawasaki disease; shock, abdominal pain or cardiac features after SARS-CoV-2 exposure raises PIMS-TS. Clinical review must respond to the whole child, not a memorised rash chart.

Key points

  • Describe blanching, lesion type, onset site, direction of spread and relationship to fever before naming an exanthem; pattern supports but rarely proves the virus.
  • Measles causes fever, cough, coryza and conjunctivitis followed by a descending maculopapular eruption; call ahead, isolate and notify the suspected case without waiting for laboratory confirmation.
  • Rubella is often mild with post-auricular or suboccipital nodes, but pregnancy exposure has urgent fetal implications and requires health-protection advice.
  • Parvovirus B19 produces bright or darker warm cheeks then a lacy limb eruption; exposure matters in pregnancy and in haemolytic disease because fetal anaemia and aplastic crisis can occur.
  • Roseola usually has several days of high fever followed by a trunk-first rash as fever settles; febrile seizures can occur during the febrile phase.
  • Hand, foot and mouth disease combines oral ulcers with lesions on palms, soles and buttocks; pain-related poor intake and dehydration are more important than rash intensity.
  • Chickenpox appears in successive crops, so macules, papules, vesicles and crusts coexist; pregnancy, neonatal age and immune compromise require urgent specialist advice.
  • In darker skin, blanching erythema may be subtle: inspect conjunctiva and mucosa, use pressure and palpation, and look for vesicles, scale, oedema and change from baseline.
  • A non-blanching rash in an unwell child is treated as sepsis until assessed; a reassuring label such as viral rash must never override physiology.
  • Antibiotics do not treat uncomplicated viral exanthems, and corticosteroid or antihistamine should not be used to conceal an undiagnosed progressive eruption.

Aetiology

01

Respiratory viral transmission

Measles, rubella, roseola and parvovirus spread mainly through respiratory secretions, with infectivity often beginning before the diagnostic eruption.

02

Enteroviral transmission

Hand, foot and mouth viruses spread through respiratory secretions, vesicle fluid and faeces, so hand hygiene remains relevant after visible lesions resolve.

03

Varicella-zoster primary infection

Airborne and direct-contact transmission causes primary varicella, after which virus persists in sensory ganglia and can later reactivate as zoster.

04

Drug and inflammatory mimic

Medicines, Kawasaki disease, PIMS-TS and bacterial toxin or invasive disease can reproduce an exanthem pattern and carry different urgency.

Pathophysiology

  1. 1
    Immune-mediated skin eruption

    Systemic viral replication and the host immune response dilate superficial vessels and recruit inflammatory cells, producing a widespread blanching maculopapular eruption.

  2. 2
    Vesicular epidermal injury

    Varicella and enteroviruses produce focal epidermal cell injury and fluid-filled lesions at characteristic mucosal, acral or centripetal distributions.

  3. 3
    Vascular leakage or coagulation failure

    In invasive infection, endothelial injury, thrombosis and consumptive coagulopathy allow blood into skin, creating fixed petechiae and purpura.

  4. 4
    Host vulnerability

    Immune compromise, neonatal immaturity, pregnancy and absent prior immunity permit greater viral replication or high-consequence fetal and organ complications.

Clinical features and red flags

MeaslesRed flag

High fever, cough, coryza and conjunctivitis precede Koplik spots and a confluent maculopapular eruption that begins behind ears or on face and spreads downward.

Rubella

Low-grade fever, fine pink or red-brown rash and tender post-auricular, posterior cervical or suboccipital nodes may be mild, while exposure during pregnancy is high consequence.

Parvovirus B19

Facial erythema is followed by a lacy or reticulate limb and trunk eruption; arthralgia may occur, and pallor or lethargy in haemolytic disease suggests aplastic crisis.

Roseola

A child aged around 6 months to 2 years has several days of abrupt high fever, then a blanching trunk rash appears as temperature and wellbeing improve.

Hand, foot and mouth disease

Painful oral vesicles or ulcers accompany grey, red-brown or violaceous papulovesicles on palms, soles and buttocks, sometimes extending beyond classic sites.

Varicella

Centripetal crops of intensely itchy superficial vesicles evolve to pustules and crusts, with lesions at several stages simultaneously and possible scalp or mucosal involvement.

Red flags requiring action

  • Non-blanching purpura, toxic appearance, altered consciousness, neck stiffness, respiratory distress, shock, severe dehydration, painful skin, blisters or mucosal erosion, focal neurology, a very young infant, immunocompromise, pregnancy exposure or fever lasting five days with Kawasaki or PIMS-TS features changes the case from routine exanthem care.

Investigations

  1. 01
    ABCDE and age-specific observationsFirst step
    Why
    Detect shock, hypoxia, encephalopathy and dehydration before classifying morphology.
    Interpretation and limitations
    Tachycardia, prolonged capillary refill, altered interaction, work of breathing or reduced urine output carries more urgency than whether a rash fits one virus perfectly.
  2. 02
    Blanching and full-skin examination
    Why
    Separate extravasated blood from vasodilatation and find diagnostically important sites.
    Interpretation and limitations
    Use firm pressure on several lesions and inspect mucosa, conjunctiva, palms and soles in good light; non-blanching supports bleeding into skin, but blanching does not exclude serious illness.
  3. 03
    Measles or rubella virology
    Why
    Confirm a suspected notifiable infection and support public-health control.
    Interpretation and limitations
    Discuss the correct oral-fluid or PCR and serology sampling with UKHSA or the local health-protection team; notify on clinical suspicion and do not wait for the result before isolation.
  4. 04
    VZV or HSV PCR
    Why
    Clarify atypical, severe, neonatal, pregnancy-associated or immunocompromised vesicular disease.
    Interpretation and limitations
    Swab the base of a fresh vesicle using appropriate precautions; a negative poor-quality crust sample does not safely exclude infection.
  5. 05
    FBC, reticulocytes and parvovirus testing
    Why
    Assess aplastic crisis in a child with chronic haemolysis or investigate a high-consequence pregnancy exposure.
    Interpretation and limitations
    A sharp haemoglobin fall with reticulocytopenia supports transient marrow arrest; select PCR or serology with haematology, obstetric or microbiology advice because timing changes interpretation.
  6. 06
    Sepsis and inflammatory work-up
    Why
    Investigate non-blanching illness, prolonged fever, shock or organ involvement.
    Interpretation and limitations
    Cultures, lactate, blood count, coagulation, renal, liver and inflammatory tests support but do not delay treatment; ECG, troponin, BNP and echocardiography are selected when Kawasaki disease or PIMS-TS is suspected.
  7. 07
    Medicine timeline
    Why
    Identify a drug eruption, DRESS or Stevens–Johnson syndrome masquerading as viral disease.
    Interpretation and limitations
    List every prescribed, over-the-counter and recent stopped medicine with first dose, last dose and rash onset; mucosal pain, blistering, facial oedema and organ injury demand urgent escalation.

Differential diagnosis

01

Meningococcal or other bacterial sepsis

Toxic appearance, abnormal perfusion and evolving non-blanching lesions override a superficially viral prodrome and demand immediate treatment.

02

Kawasaki disease or PIMS-TS

Persistent fever with mucocutaneous inflammation, extremity change, gastrointestinal symptoms, shock or cardiac findings needs a dedicated inflammatory pathway.

03

Drug eruption or SJS/TEN

A medicine timeline, skin pain, target lesions, facial oedema, mucosal erosions, blisters and organ injury distinguish dangerous drug reactions.

04

Scarlet fever

Sore throat, strawberry tongue, sandpaper texture and flexural accentuation support group-A streptococcal toxin disease and antibiotic treatment.

05

Gianotti–Crosti and pityriasis rosea

Well-child acral papules or a herald patch followed by cleavage-line scale may follow infection but lack the systemic and transmission priorities of classic exanthems.

Additional chapter-specific clues

Dangerous mimicRed flag

Fixed purpura with systemic illness, painful targetoid blistering with mucositis, prolonged fever with inflammatory signs or focal neurological change is not a routine self-limiting exanthem.

Management

01Immediate-danger routeTreat physiology before patternFirst stepThe child is toxic, shocked, neurologically abnormal, severely dehydrated or has non-blanching purpura or mucosal skin failure.+
  1. 1Perform ABCDE assessment, obtain senior paediatric help and isolate where an airborne or contact-transmitted infection is plausible.
  2. 2Give age-specific sepsis and meningococcal treatment, fluids, oxygen and airway support without waiting for rash evolution or test results.
  3. 3EscalationEscalate painful blistering to specialist skin-failure care and prolonged inflammatory fever to Kawasaki or PIMS-TS assessment.
02Suspected measlesCall, isolate and notifyFever, cough, coryza or conjunctivitis accompanies a descending rash or there is a compatible exposure.+
  1. 1Ask the family not to enter a shared waiting area, notify the clinical facility before arrival and apply airborne infection-control arrangements.
  2. 2ConfirmatoryNotify the proper officer or health-protection team promptly on clinical suspicion and obtain recommended confirmatory samples without delaying public-health action.
  3. 3Assess for pneumonia, dehydration, otitis, encephalitis and vitamin-A or nutritional vulnerability and give exclusion and susceptible-contact advice through the health-protection team.
03Supportive-care routeRelieve symptoms and protect hydrationA well child has a coherent uncomplicated roseola, hand-foot-and-mouth, parvovirus or varicella pattern.+
  1. 1Encourage frequent cool fluids and age-safe feeds, use simple analgesia for distress and oral pain and keep nails short for an itchy vesicular eruption.
  2. 2Avoid aspirin in children, avoid ibuprofen in chickenpox unless specifically advised and do not prescribe antibiotics without bacterial infection.
  3. 3Give condition-specific school or childcare and contact advice plus explicit return precautions for breathing, alertness, hydration, persistent fever, non-blanching lesions or skin pain.
04High-risk-contact routeAct before complications appearThe case or close contact is pregnant, a neonate, immunocompromised or has chronic haemolytic disease.+
  1. 1Identify the likely virus and exact exposure timing and seek same-day microbiology, obstetric, neonatal, haematology or infectious-disease advice.
  2. 2Check documented immunity or targeted serology as advised and arrange time-dependent post-exposure prophylaxis or monitoring rather than waiting for a rash.
  3. 3For parvovirus exposure assess maternal and fetal or haemolysis risk; for varicella or measles follow the current UKHSA immunoglobulin, antiviral or vaccination pathway.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Relieves pain and distress while fluids and observation address the main needs of an uncomplicated viral illness.

Paracetamol for fever-related distress

Use the child's age- or weight-appropriate licensed oral dose and interval shown in the current product information; do not exceed the stated 24-hour maximum and check combination cold remedies for duplicate paracetamol.

Treat the child rather than temperature alone. Dose carefully in underweight children, liver disease or prolonged poor intake, and do not let temporary improvement delay review of shock, altered consciousness or dehydration.

Limits VZV replication in groups at high risk of disseminated, neurological, pulmonary or neonatal disease.

Aciclovir for high-risk or complicated varicella

Use only after urgent specialist assessment, with route and dose adjusted for age, weight, immune status, renal function and time from rash onset; severe, neonatal or immunocompromised disease generally requires intravenous paediatric treatment.

Ordinary chickenpox in a well otherwise healthy young child usually needs supportive care. Ensure hydration, adjust for renal impairment and coordinate pregnancy, neonatal and immunocompromised exposure prophylaxis with current UKHSA guidance.

Complications

01

Measles organ disease

Otitis, pneumonia, diarrhoea, acute encephalitis and later subacute sclerosing panencephalitis account for important childhood morbidity and mortality.

02

Varicella dissemination

Bacterial superinfection, pneumonia, cerebellitis, encephalitis and visceral disease are more likely in adults, pregnancy and immune compromise.

03

Parvovirus haematological and fetal effects

Transient red-cell aplasia can cause severe anaemia in chronic haemolysis, while fetal infection can cause anaemia, hydrops or loss.

04

Dehydration and febrile seizure

Painful oral disease limits fluids, and rapid fever rise in roseola or another infection can precipitate a febrile seizure.

05

Transmission to vulnerable people

A mild or pre-rash infection can expose unvaccinated, pregnant, neonatal or immunocompromised contacts before the diagnosis is recognised.

Monitoring and follow-up

  • Tell caregivers to reassess breathing, alertness, fluid intake, urine output, skin pain, blanching and fever duration rather than counting spots alone.
  • Arrange early review for infants, immunocompromised children and anyone with worsening after initial improvement, secondary bacterial change or persistent high fever.
  • For suspected measles or rubella confirm that notification, specimen result, infection-control advice and vulnerable-contact tracing have named owners.
  • After parvovirus exposure in pregnancy or haemolytic disease, verify obstetric ultrasound or haematology follow-up rather than offering reassurance when the rash fades.
  • In varicella, seek urgent review for breathing difficulty, severe headache, ataxia, persistent fever, spreading painful erythema or pregnancy, neonatal or immune vulnerability.
  • Document medicine exposures and stop decisions when a severe drug eruption is possible and ensure organ monitoring continues even after the skin begins to improve.

Special situations

The fever–rash sequence helps

Roseola classically erupts as fever resolves, whereas measles rash arrives during continuing systemic illness; the relationship is more useful than colour alone.

Crops distinguish varicella

Simultaneous macules, papules, vesicles and crusts reflect repeated crops and help distinguish chickenpox from many monomorphic vesicular disorders.

A glass test is one observation

Non-blanching demands escalation in an unwell child, but a blanching rash cannot certify that circulation and infection risk are normal.

The mild child may have a high-risk contact

Rubella, parvovirus and varicella can be uncomplicated in the child but consequential for a pregnant, fetal, neonatal or immunocompromised contact.

Notification precedes certainty

Clinical suspicion of measles triggers notification and infection control because waiting for confirmation permits avoidable exposure.

Skin tone changes visibility, not danger

Purpura, vesicles, warmth, mucosal disease and physiological deterioration remain detectable when erythema is subtle, especially with good light and palpation.

Common pitfalls

  1. 01

    Calling a febrile rash viral before recording observations, blanching, mucosa and neurological state.

  2. 02

    Sending a possible measles case into a crowded waiting room without advance warning.

  3. 03

    Waiting for virology before notifying a clinically suspected measles case.

  4. 04

    Using absence of a non-blanching rash to exclude sepsis or meningococcal disease.

  5. 05

    Giving ibuprofen routinely during chickenpox or aspirin to a child with viral illness.

  6. 06

    Missing pregnancy, neonatal, immunocompromised or chronic-haemolysis contacts who need time-sensitive advice.

  7. 07

    Treating painful mucositis and blistering as an ordinary viral exanthem without reviewing the medicine timeline and skin-failure risk.