What is the treatment for Scarlet Fever?

Scarlet Fever: Pathogen and Treatment

Pathogen

The causative pathogen is Streptococcus pyogenes (Group A Streptococcus), which produces pyrogenic exotoxins responsible for the characteristic clinical presentation. 1, 2, 3

Clinical Presentation Confirmation

The classic triad you've described confirms scarlet fever:

• Fever (typically ≥38°C/102°F) 1, 2
• Sore throat with tonsillopharyngeal erythema, often with exudates 2
• Sandpaper-like rash (fine papular eruption), often with perineal accentuation 2
• Strawberry tongue (initially white-coated, then bright red with prominent papillae) 2, 3

This presentation distinguishes scarlet fever from Kawasaki disease (which lacks exudative pharyngitis and doesn't respond rapidly to antibiotics) and viral pharyngitis (which rarely presents without cough, hoarseness, or conjunctivitis). 2

First-Line Treatment

Oral Penicillin V (phenoxymethylpenicillin) is the treatment of choice: 1, 4

Dosing Regimen

For children weighing <40 kg:

• Mild to moderate infections: 25 mg/kg/day divided every 12 hours OR 20 mg/kg/day divided every 8 hours 5
• Severe infections: 45 mg/kg/day divided every 12 hours OR 40 mg/kg/day divided every 8 hours 5

For children ≥40 kg and adults:

• 250-500 mg every 6-8 hours for 10 days 1
• Alternatively: 500 mg twice daily or 250 mg three times daily 6

Critical: Treatment must continue for a full 10 days to prevent acute rheumatic fever, even after symptoms resolve. 6, 5

Alternative Antibiotics

For patients with non-anaphylactic penicillin allergy:

• First-generation cephalosporins (e.g., cephalexin) are recommended 1

For patients with true penicillin allergy (anaphylaxis or severe hypersensitivity):

• Macrolides (e.g., azithromycin, clarithromycin) are recommended 1
• Important caveat: Some S. pyogenes strains show macrolide resistance, so monitor clinical response closely 1

Amoxicillin is an acceptable alternative:

• Same dosing as penicillin V, with better gastrointestinal tolerance when taken with meals 5

Critical Management Points

Timing of antibiotic initiation:

• Antibiotics can be started up to 9 days after symptom onset and still prevent rheumatic fever 6
• However, early treatment reduces infectivity period and morbidity 6
• Patient becomes non-contagious after 24 hours of antibiotic therapy 6

Expected clinical response:

• Fever should resolve within 48-72 hours of starting antibiotics 1
• If symptoms persist beyond 3-5 days of appropriate antibiotic therapy, reassess the diagnosis and consider alternative pathogens 1

Common Pitfalls to Avoid

Never use sulfonamide antibiotics (including trimethoprim-sulfamethoxazole):

• These are associated with increased disease severity and mortality in streptococcal infections 6

Never use aspirin for fever control in children:

• Risk of Reye's syndrome in patients under 16 years 1

Do not routinely culture or treat asymptomatic household contacts:

• Only culture and treat contacts during outbreak situations with documented positive cultures 1

Post-treatment throat cultures are not routinely needed:

• Only perform if symptoms persist or recur 1

Complications if Untreated

Early antibiotic treatment is essential to prevent serious sequelae:

• Acute rheumatic fever 7, 3
• Post-streptococcal glomerulonephritis 7, 3
• Bacteremia and sepsis 7
• Pneumonia 7
• Endocarditis 3
• Meningitis 7