Suggest Treatment For Bumpy Rash On Left Arm Below The Elbow

Hi, my 4 yo daughter has developed bumpy rash on her left arm below the elbow for the past 5 days. I am a single parent (Dad) and I sometimes have to take her with me to work or rarely on trips, but this has not been the case for the past month. A general practitioner gave her a betametasone 0.01 treatment but it aggrevated her symptoms. I really appreciate your help and thanks in advance. Camron