Scarlet fever is a syndrome caused by infection with toxin-producing group A β‑hemolytic streptococci (Streptococcus pyogenes, GAS) and primarily affects children between the ages of five and fifteen. The syndrome occurs in less than 10% of cases of streptococcal tonsillopharyngitis and classically presents with fever, pharyngeal erythema with tonsillar exudates, and a fine, scarlet-colored rash that is most pronounced in the groin, underarm, and elbow creases. After approximately a week, the skin begins to desquamate on the face, trunk, hands, fingers, and toes. Antibiotic treatment with penicillin is recommended, as scarlet fever may progress to severe disease and other complications associated with Streptococcus infection (e.g., rheumatic fever and post‑streptococcal glomerulonephritis). Scarlet fever is caused by various types of erythrogenic scarlet fever toxins, secreted by S. pyogenes and as such, recurrent infection with other types of toxins is possible.
- Peak incidence: 5–15 years (although it may affect individuals of any age) 
- Generally occurs in association with streptococcal cases of tonsillopharyngitis
Epidemiological data refers to the US, unless otherwise specified.
- Route of transmission: aerosol
- 2–5 days 
Initial phase ()
- Malaise, headache, chills, and myalgias
- Gastrointestinal symptoms (possible in young children)
- Rash appears 12–48 hours after the onset of fever. 
Scarlet‑colored maculopapular exanthem (rash)
- Begins on the neck
- Disseminates to the trunk and extremities
- Duration: ∼ 7 days 
- Pharyngeal erythema, possibly with tonsillar exudates
- Strawberry tongue: bright red tongue color with papillary hyperplasia, which is revealed once the white coating has sloughed off
- Typical red, flushed appearance of the cheeks with perioral pallor
- Appears 7–10 days after resolution of rash 
- Skin desquamation: desquamation of the skin in flakes
- Affects face, trunk, hands, fingers, and toes
Scarlet fever is primarily a clinical diagnosis that should be confirmed with additional testing.
- Pathogen detection
- Blood and urine studies
- Other tests
- Classic pediatric exanthem diseases
- Drug hypersensitivity reaction
- Viral tonsillitis (infectious mononucleosis, herpangina)
The differential diagnoses listed here are not exhaustive.
- Indication: All cases of scarlet fever should be treated with antibiotics, both to prevent complications and to prevent transmission.
- Drug of choice: oral penicillin V
- Alternative antibiotics
- After 24 hours of antibiotic treatment, the patient is no longer infectious and may return to daycare or school. 
Scarlet fever is considered one of the nonsuppurative (i.e., non-pus forming) complications of streptococcal tonsillopharyngitis. Other complications of GAS infection may also occur during or following scarlet fever, especially in patients who did not receive antibiotic treatment.
- Poststreptococcal glomerulonephritis
Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS) 
- Definition: a rare disorder that is characterized by sudden onset or exacerbation of OCD) and/or a following infection with S. pyogenes (
- Clinical features
- Diagnostic criteria 
Suppurative (i.e., pus-forming)
We list the most important complications. The selection is not exhaustive.