Scarlet fever generally requires isolation for at least seven days, which is to prevent the spread of scarlet fever to other children. The period of isolation for scarlet fever is judged mainly on the basis of whether the contagiousness of scarlet fever has disappeared or not. However, there is no practical and effective clinical method that can accurately discern when the contagiousness of scarlet fever disappears, so it needs to be seen in a combination of several aspects, as follows: first, look at the symptoms of scarlet fever. If the symptoms of scarlet fever have not completely disappeared, scarlet fever is considered to be still contagious, and only when If the symptoms of scarlet fever have not disappeared completely, the contagiousness may disappear. Second, the duration of the scarlet fever should be determined. If the fever is within seven days, the fever is still considered to be contagious, and only if the fever is greater than seven days does the contagiousness disappear. Thirdly, if the bacterial culture can produce Streptococcus haemolyticus, the disease is still considered infectious, but the positive rate of Streptococcus haemolyticus in the throat swab is very low. In clinical practice, the method of ruling out the infectiousness of scarlet fever by means of a pharyngeal swab is not particularly common, so only the first two aspects can be combined to determine roughly whether the infectiousness of scarlet fever has disappeared, and the isolation period can only last for at least seven days.