Most of the rashes in this age group are due to allergic in origin.
I hope this will resolve with the treatment prescribed. If symptoms persists then other systemic causes of rashes must be ruled be ruled out by thorough evaluation.
So I would suggest you to continue the medication also give some antacid
if not prescribed already.
Watch for the resolution or progression of the symptoms. If symptoms persists then consult a pediatrician
for further evaluation.
Avoid allergens like dust, pollens, air freshners, perfumes and any food items if he is allergic to any.