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Scarlet fever and group-A streptococcal disease

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

RapidFull
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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.

Overview

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.

Group-A Streptococcus is Streptococcus pyogenes, a human throat and skin pathogen. Disease ranges from asymptomatic carriage and local pharyngitis to toxin-mediated scarlet fever, invasive soft-tissue infection, bacteraemia and post-infectious immune disease.

Scarlet fever occurs when a susceptible host responds to streptococcal pyrogenic exotoxin. The rash reflects toxin effects rather than bloodstream invasion, so a dramatic sandpaper eruption can coexist with otherwise uncomplicated pharyngitis.

Transmission is through respiratory droplets, close contact and contaminated secretions. Crowding in households, schools and nurseries supports outbreaks; skin disease and varicella lesions provide separate portals for invasive infection.

Take a chronological history of sore throat, rash onset, pain, fever, swallowing, breathing and treatment. Ask about chickenpox, influenza, wounds, surgery, household illness, school cluster, previous rheumatic fever and antimicrobial allergy details.

Practice

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Paediatrics and child healthOriginal SBA

Scarlet-fever eradication course

A 4-year-old has fever, pharyngitis, strawberry tongue and a flexurally accentuated sandpaper rash, with no penicillin allergy. Which treatment is preferred?

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.

  • 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 ·

Examine physiological stability first. Then inspect tonsils, palate and tongue, palpate cervical nodes, feel the rash texture, inspect flexures and perioral region, and look for impetigo, varicella lesions, wound infection or focal limb swelling.

Rash colour may be subtle on darker skin, but rough texture, flexural prominence, strawberry tongue and desquamation remain detectable. Palpation and mucosal examination are therefore central.

A classic uncomplicated case needs no blood test or imaging. Swabbing is most useful when the phenotype is uncertain, antibiotics have not yet started, or public health needs confirmation during a cluster.

A positive throat culture does not prove that GAS causes every symptom because carriage occurs. Interpret it with pharyngitis and toxin-rash features, and reconsider measles, EBV, Kawasaki disease or drug reaction when the sequence is atypical.

Penicillin remains predictably active against GAS. Ten-day phenoxymethylpenicillin treatment for scarlet fever improves recovery, reduces transmission and increases eradication; completion matters even after rapid symptomatic improvement.

Invasive disease requires a different scale of care. Antibiotics must cover the likely focus and sepsis context, while early drainage, debridement or joint washout controls bacterial burden. A toxin-suppressing agent may be added by infection specialists.

Scarlet fever is notifiable in England. Public-health teams link cases, identify outbreaks and coordinate action; children return to school or nursery only after at least 24 hours of appropriate antibiotic treatment.

After an invasive case, contact management is risk-based. Defined contacts may receive antibiotics and all close contacts need clear advice about symptoms during the surveillance period, because risk is concentrated soon after the index diagnosis.

Key points

  • 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.

Aetiology

01

Toxigenic pharyngeal GAS

A strain producing streptococcal pyrogenic exotoxin causes scarlet fever when infecting a child without neutralising antitoxin immunity.

02

Skin barrier disruption

Varicella, eczema, wounds, burns and surgery allow GAS to invade subcutaneous tissue, fascia, muscle or bloodstream.

03

Respiratory transmission

Droplets and close contact spread throat organisms efficiently within households, classrooms and nurseries, supporting seasonal clusters.

04

Host susceptibility

Young age, recent viral infection, immune compromise and close exposure influence acquisition, toxin response and invasive-disease risk.

Pathophysiology

  1. 1
    Exotoxin-mediated rash

    Circulating pyrogenic exotoxin drives fever and diffuse capillary skin inflammation, creating rough erythema and flexural accentuation.

  2. 2
    Local suppuration

    Untreated or progressive throat and skin infection can extend into adjacent tissue, forming abscess, cellulitis or deep neck infection.

  3. 3
    Fascial tissue destruction

    Invasive organisms and enzymes spread rapidly along fascial planes, causing thrombosis, necrosis and severe pain before obvious surface change.

  4. 4
    Superantigen shock

    Streptococcal superantigens activate unusually large T-cell populations, producing cytokine release, vasodilatation, capillary leak and multiorgan failure.

  5. 5
    Post-infectious autoimmunity

    Cross-reactive antibodies or immune complexes can later inflame heart, joints, nervous system or glomeruli after the original infection resolves.

Clinical features and red flags

Scarlet-fever triad

Link fever and pharyngitis to a fine rough rash, strawberry tongue, flexural Pastia lines and circumoral pallor.

Rash evolution

Establish that the rash followed the systemic illness by 12 to 48 hours and later may peel at fingers and toes.

Airway and neck screen

Assess voice, drooling, trismus, stridor, neck movement and swelling for peritonsillar or retropharyngeal extension.

Invasive pain phenotype

Seek severe focal pain, rapid progression, swelling, bullae, crepitus and anaesthesia, including beneath varicella lesions.

Shock phenotype

Document perfusion, mental state, respiratory effort, urine output and lactate; hypotension is a late paediatric sign.

Exposure pattern

Record household, school or nursery cases and recent invasive-GAS contact for notification, outbreak and prophylaxis decisions.

Red flags requiring action

  • 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.

Investigations

  1. 01
    First-line: clinical examinationFirst stepFirst line
    Why
    Identify the classic scarlet-fever phenotype and screen for invasive or deep complications.
    Interpretation and limitations
    Sandpaper texture, strawberry tongue and flexural accentuation support diagnosis; instability or disproportionate pain redirects immediately to sepsis care.
  2. 02
    Throat swab when diagnosis is uncertain
    Why
    Culture GAS before antibiotics when confirmation will change clinical or outbreak management.
    Interpretation and limitations
    A positive result supports infection in the right phenotype but may represent carriage; do not delay treatment of a convincing case.
  3. 03
    First-line invasive-disease culturesFirst line
    Why
    Identify GAS in blood or a normally sterile focus and provide susceptibility data.
    Interpretation and limitations
    Take blood and deep source samples before antibiotics when this causes no delay; superficial swabs may not represent fascial infection.
  4. 04
    Sepsis and organ-function panel
    Why
    Assess perfusion, inflammation, coagulation, kidney, liver and muscle injury in systemic disease.
    Interpretation and limitations
    Use blood gas and lactate, full blood count, C-reactive protein, renal and liver tests, coagulation and creatine kinase; trends guide escalation.
  5. 05
    Targeted imaging and surgical exploration
    Why
    Locate abscess, bone or joint infection and define tissue requiring source control.
    Interpretation and limitations
    Ultrasound or cross-sectional imaging can help a stable child, but suspected necrotising infection is a surgical emergency and imaging must not delay exploration.

Differential diagnosis

01

Viral exanthem

Cough, coryza, conjunctivitis, vesicles or a fever-rash sequence inconsistent with scarlet fever supports measles, enterovirus or another virus.

02

Kawasaki disease

Five days of fever with non-purulent conjunctivitis, oral change, extremity change and cervical nodes requires urgent coronary-risk assessment.

03

Drug eruption

A recent medicine, symmetrical morbilliform rash and absent streptococcal pharyngitis may indicate a drug reaction, including severe mucosal disease.

04

Staphylococcal toxin disease

Bullae, superficial tenderness, peeling, hypotension or a device-related focus instead suggests staphylococcal scalded-skin or toxic-shock syndrome.

05

Epstein-Barr virus

Marked fatigue, posterior cervical nodes, hepatosplenomegaly and atypical lymphocytes support infectious mononucleosis; aminopenicillin can provoke a prominent rash.

Management

01UncomplicatedTreat scarlet fever for ten daysFirst stepThe child has the classic scarlet-fever phenotype without invasive or airway features.+
  1. 1AlternativeStart age-banded oral phenoxymethylpenicillin for 10 days; use a current allergy alternative when genuinely needed.
  2. 2Give fluids and suitable analgesia, explain that symptoms improve before bacterial eradication and require the full course.
  3. 3Notify public health, exclude from school or nursery until 24 hours after antibiotics begin and safety-net for invasive symptoms.
02UncertainSwab without delaying careThe rash or throat phenotype is atypical, or confirmation is important for an outbreak.+
  1. 1Take a throat swab before the first antibiotic dose when practical and provide the health protection team with cluster details.
  2. 2Treat immediately when clinical suspicion remains convincing rather than waiting for culture.
  3. 3Review the result with symptoms and carriage probability, changing or stopping treatment only when the whole diagnosis supports it.
03InvasiveResuscitate and control the sourceSevere pain, rapid tissue progression, shock or a sterile-site focus suggests invasive GAS.+
  1. 1Activate the paediatric sepsis pathway, obtain blood and deep cultures and give immediate broad-spectrum intravenous antibiotics.
  2. 2Request emergency surgical, orthopaedic, ENT or other source-control assessment according to the focus.
  3. 3DefinitiveEscalationAdd definitive penicillin and toxin-suppressing therapy with infection-specialist advice, and escalate organ support to paediatric critical care.
04ContactsUse health-protection risk assessmentAn invasive GAS case or linked scarlet-fever cluster is identified.+
  1. 1Notify the health protection team and provide case, setting, diagnosis date and contact information promptly.
  2. 2Assess symptomatic contacts clinically and let public health define which asymptomatic close contacts require chemoprophylaxis.
  3. 3Give all defined close contacts clear 30-day symptom-surveillance advice and urgent access instructions.
Key medicines and prescribing safety3 treatments · regimens, roles and cautions+
First-choice eradication treatment for uncomplicated scarlet fever and susceptible GAS pharyngitis.

Phenoxymethylpenicillin

Give 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.

Macrolide alternative when penicillin cannot safely be used and eradication treatment is required.

Clarithromycin

For 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.

Definitive systemic and toxin-directed treatment for sterile-site infection, necrotising disease or streptococcal toxic shock.

Intravenous therapy for invasive GAS

Give the immediate local paediatric sepsis regimen, then use current BNFC age-and-weight intravenous benzylpenicillin plus a toxin-suppressing agent such as clindamycin when infection specialists confirm the indication.

Do not delay surgery for additional antibiotic doses. Check renal and hepatic function, allergy, culture susceptibility, clindamycin-associated diarrhoea and the need to retain broader polymicrobial cover.

Complications

01

Deep suppurative infection

Peritonsillar, retropharyngeal or other abscess can compromise swallowing or airway and requires imaging, drainage and intravenous therapy.

02

Necrotising soft-tissue infection

Rapid fascial spread causes extensive tissue death, bacteraemia, shock and limb-threatening injury requiring immediate emergency surgery.

03

Streptococcal toxic shock

Toxin-mediated shock with organ dysfunction can accompany an initially small or hidden soft-tissue, uterine or pulmonary focus.

04

Acute rheumatic fever

Delayed cross-reactive inflammation can affect heart, joints, skin and nervous system, with carditis creating chronic valve damage.

05

Post-streptococcal glomerulonephritis

Immune-complex renal inflammation causes haematuria, oedema, hypertension and reduced filtration several weeks after throat or skin infection.

Monitoring and follow-up

  • Expect fever and systemic symptoms to begin improving within about 24 hours of effective uncomplicated treatment; reassess persistence or deterioration.
  • Check oral intake, urine output, airway symptoms, rash progression and new focal pain during the first 48 hours.
  • Confirm completion of the full 10-day penicillin course and correct 24-hour exclusion advice with family and setting.
  • In invasive disease, trend perfusion, lactate, coagulation, creatine kinase, renal and liver function and tissue viability during source-control treatment.
  • Review cultures and susceptibilities promptly, particularly with a macrolide, and narrow the systemic regimen only when all foci are controlled.
  • Advise later review for migratory joint pain, breathlessness, murmur, choreiform movement, dark urine, oedema or reduced urine output.
  • Close contacts managed through the invasive-GAS pathway need clear surveillance for 30 days after the index diagnosis.

Special situations

Texture outlasts colour uncertainty

Sandpaper feel, Pastia lines and strawberry tongue help recognise scarlet fever when erythema is less visible on darker skin.

Pain can be the earliest invasion clue

Necrotising infection may cause profound pain before swelling, blistering or skin discoloration becomes dramatic.

Ten days has a public-health purpose

The scarlet-fever course aims for GAS eradication and reduced transmission, not only rapid relief of sore throat.

Positive throat swabs need context

Asymptomatic carriage means a detected organism does not prove that an atypical rash is scarlet fever.

Antibiotics cannot replace debridement

Necrotic or closed-space infection retains high bacterial and toxin burden until urgent source control occurs.

Common pitfalls

  1. 01

    Do not rely on rash colour alone; palpate for sandpaper texture and inspect the tongue and flexures.

  2. 02

    Do not use a five-day sore-throat penicillin course for confirmed scarlet fever when the recommended eradication course is 10 days.

  3. 03

    Do not delay treatment of a convincing case while waiting for a throat culture.

  4. 04

    Do not label severe pain during or after chickenpox as simple viral myalgia without examining for invasive GAS.

  5. 05

    Do not wait for hypotension or skin necrosis before escalating possible streptococcal toxic shock.

  6. 06

    Do not let imaging delay surgical exploration when necrotising infection is strongly suspected.

  7. 07

    Do not prescribe prophylaxis to every contact without health-protection risk assessment.

  8. 08

    Do not forget delayed rheumatic and renal symptoms after the acute throat or skin illness has resolved.

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