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Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

Scarlet fever and group-A streptococcal disease

Paediatrics and child health · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Possible invasive group-A streptococcal infection

Shock, severe pain out of proportion, rapidly progressive swelling, soft-tissue crepitus, breathing difficulty, altered consciousness or deterioration during chickenpox can indicate necrotising infection, streptococcal toxic shock or another invasive GAS focus.

Action: Activate the paediatric sepsis response, obtain blood and source cultures without delaying broad-spectrum intravenous antibiotics, and involve paediatric critical care. Seek immediate surgical assessment for possible necrotising infection or an undrained focus; add organism- and toxin-directed therapy with infection-specialist advice.

Synopsis

Recognise scarlet fever and the wider group-A streptococcal spectrum, distinguish uncomplicated toxin-mediated disease from invasive infection, prescribe eradication treatment correctly, and complete notification and contact actions.

  • Scarlet fever is toxin-mediated Streptococcus pyogenes infection, usually pharyngitis, with fever, sore throat and a fine blanching sandpaper rash appearing about 12 to 48 hours later.
  • The rash often begins on trunk or groin, accentuates in flexures as Pastia lines, spares the area around the mouth and may be followed by fingertip or toe desquamation.
  • A white-coated then red strawberry tongue, tender anterior cervical nodes and tonsillar inflammation support the diagnosis; cough, coryza and conjunctivitis favour a viral alternative.
  • Diagnose a classic case clinically. Take a throat swab before antibiotics when the diagnosis is uncertain or public health requests it, but do not wait for culture to treat a convincing case.
  • First-line scarlet-fever treatment is oral phenoxymethylpenicillin for 10 days. Use the exact age-banded dose and stress completion even when fever resolves within 24 hours.
  • For true penicillin allergy, use the current UKHSA or local macrolide regimen and check interactions and susceptibility; resistance makes penicillin-allergy history clinically important.
  • Notify scarlet fever promptly and provide school or nursery details. Exclude the child until 24 hours after appropriate antibiotics have started.
  • Do not routinely test or treat well household contacts of a single uncomplicated case, but assess symptomatic contacts and follow health-protection advice during outbreaks.
  • GAS also causes impetigo, cellulitis, perianal disease, pneumonia, septic arthritis and osteomyelitis; invasive disease is defined by infection in a normally sterile site or a severe toxin-mediated syndrome.
  • Severe focal pain, rapid progression, shock or soft-tissue signs requires sepsis antibiotics and immediate source-control assessment, not an oral scarlet-fever regimen.
  • Suppurative complications include otitis, sinusitis and peritonsillar or retropharyngeal abscess; delayed immune complications include acute rheumatic fever and post-streptococcal glomerulonephritis.
  • Health protection risk-assesses close contacts of invasive GAS for chemoprophylaxis and 30-day symptom surveillance; do not prescribe indiscriminately outside that pathway.

Key red flags

Pain out of proportion to visible skin change, rapidly spreading swelling, bullae, anaesthesia, crepitus or systemic toxicity requires immediate surgical and sepsis assessment.

Mottling, prolonged capillary refill, reduced urine output, hypotension, altered consciousness or rising lactate suggests streptococcal toxic shock or invasive sepsis.

A child with chickenpox or recent influenza who develops recurrent fever, focal severe pain or rapid deterioration has increased risk of invasive GAS.

Respiratory distress, drooling, stridor, trismus, torticollis or neck swelling suggests a deep airway or neck-space complication rather than uncomplicated scarlet fever.

Persistent fever despite appropriate treatment, focal bone or joint pain, a new murmur or neurological features requires assessment for a metastatic or deep focus.

A close contact of invasive GAS who becomes unwell within the surveillance period needs urgent clinical assessment and health-protection linkage.

Investigation priorities

01
First-line: clinical examinationFirst stepFirst line

Identify the classic scarlet-fever phenotype and screen for invasive or deep complications.

02
First-line invasive-disease culturesFirst line

Identify GAS in blood or a normally sterile focus and provide susceptibility data.

Management branches

UncomplicatedTreat scarlet fever for ten days

The child has the classic scarlet-fever phenotype without invasive or airway features.

  1. Start age-banded oral phenoxymethylpenicillin for 10 days; use a current allergy alternative when genuinely needed.
  2. Give fluids and suitable analgesia, explain that symptoms improve before bacterial eradication and require the full course.
  3. Notify public health, exclude from school or nursery until 24 hours after antibiotics begin and safety-net for invasive symptoms.

Key medicines

PhenoxymethylpenicillinGive orally for 10 days: age 1–11 months 62.5 mg four times daily or 125 mg twice daily; 1–5 years 125 mg four times daily or 250 mg twice daily; 6–11 years 250 mg four times daily or 500 mg twice daily; 12–17 years 500 mg four times daily or 1 g twice daily.Verify age, allergy phenotype, swallowing and adherence. A shorter sore-throat course is not the scarlet-fever public-health regimen; severe systemic or deep infection needs intravenous treatment and source control.
ClarithromycinFor true penicillin allergy in scarlet fever, give the current BNFC age-and-weight oral dose for 10 days, following UKHSA outbreak guidance and local susceptibility advice.Check QT prolongation, hepatic impairment and CYP3A interactions. Review susceptibility when available because macrolide resistance occurs; clarify vague allergy labels rather than defaulting automatically.
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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.

  • UKHSA scarlet-fever outbreak guidanceClinical phenotype, ten-day treatment, notification, exclusion and cluster management.
  • NICE NG84 acute sore-throat prescribingAge-banded phenoxymethylpenicillin and macrolide doses and antimicrobial-safety considerations.
  • UKHSA invasive-GAS contact guidanceDefinitions, prophylaxis eligibility and symptom surveillance for close community contacts.
  • UKHSA GAS activity 2025 to 2026Current penicillin susceptibility, severe-disease vigilance and varicella-associated invasive risk.
  • NICE NG254 paediatric sepsis managementEmergency assessment, culture, antibiotic timing, fluids and critical-care escalation for invasive infection.

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

Content changes
Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom