Childhood viral exanthems — Rapid

Synopsis

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.

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.

Key red flags

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.

Measles

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

Dangerous mimic

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.

Investigation priorities

ABCDE and age-specific observationsFirst step

Detect shock, hypoxia, encephalopathy and dehydration before classifying morphology.

Management branches

Immediate-danger routeTreat physiology before pattern

The child is toxic, shocked, neurologically abnormal, severely dehydrated or has non-blanching purpura or mucosal skin failure.

Perform ABCDE assessment, obtain senior paediatric help and isolate where an airborne or contact-transmitted infection is plausible.
Give age-specific sepsis and meningococcal treatment, fluids, oxygen and airway support without waiting for rash evolution or test results.
Escalate painful blistering to specialist skin-failure care and prolonged inflammatory fever to Kawasaki or PIMS-TS assessment.

Key medicines

Paracetamol for fever-related distressUse 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.

Aciclovir for high-risk or complicated varicellaUse 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.

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