The incubation period between contracting strep and the onset of scarlet fever is short, typically 72 hours but may range from 1 to 7 days. Illness usually begins with a fever and sore throat and may be accompanied by chills, vomiting, abdominal pain and malaise.
The strep bacteria produces a toxin that causes a rash that appears 1 to 2 days after the onset of illness. The rash initially appears on the neck and chest, then spreads over the body. Typically the rash begins as small red macules which gradually become elevated. The redness fades over a few days and the patient is left with a rough "sandpaper" feeling rash. While the rash is still red the patient may develop what are called Pastia's lines, bright red coloration of the creases under the arm and in the groin. The rash usually lasts for 3 days. As the rash fades, desquamation (peeling) may occur around the finger tips, toes, and groin area.
The throat culture should be positive for group A Strep. There is a rapid antigen test (throat swab).
Therapy is designed to treat the infection with antibiotics (usually penicillin) and relieve symptoms with analgesics, rest, and plenty of fluids. Scarlet fever is usually not a serious illness when treated promptly. Improvement typically begins within 24 hours of starting treatment. Very rarely do the bacteria spread to other parts of the body. If it does, the result may be ear infections, sinusitis, glomerulonephritis or rheumatic fever.