Suggest Treatment For An Itchy Skin Rash All Over The Body

Hi I have a 15yr old girl who has had a sudden onset of an itchy rash 2 wks ago. The rash was predominantly on her torso but has now developed spots on her arms, legs, neck, hair and on to her face. The rash is red, very itchy, some some, some raised. Each day she is developing more spots. Also she is very lethargic since a wk before the spots started.