How Can Rashes On Scalp And Ears Of A Child Be Treated?

hello, from last thursday night my son developed frine rash on his cheek,by the morning it was all over his face and torso, on friday it got worse every inch of his body is covered in them down to his legs, under his scalp,his ear and also very itchy. when i took him to the gp on friday the dr said his throat was red and gave him anti-biotic to take he said the rash should go down within the next 48hrs the antiobiotics was to be taken 4 timeas a day for 5 days. its now monday and there is no improvement whatsoever and seems to be getting worse.