My 14 year old daughter manifested rash for a couple days before we got her to the doctor (thought it was contact dermatitis at first). The doctor prescribed Z-Pak (azithromycin) for scarlet fever, empirically based on appearance of rash. They used ibuprofen for fever, Benadryl to help with itchy sensations as well as some sinus drainage, pseudoephedrine for sinuses as well. Low grade fever subsided by the end of day 2 of treatment, she had still some queasiness on day 3, and was back to school on day 4. Rash actually appeared to spread/accentuate for a couple days after start of treatment. If I understand correctly, this article states rash could persist for quite some time after the 5 day treatment ends.

For scarlet fever my daughter received amoxicillin.