Sudden rash

A 2-year-old boy was brought to the clinic by his mother for the evaluation of rash on his face. He has a history of atopic dermatitis (AD) that flared 9 days ago and was given hydrocortisone and emollient. His mother says at first, the rash became better, but suddenly 3 days ago, he developed a new rash that is getting worse. He is the only child and his vaccinations are up to date. Vital signs are normal except for fever (38.5 ⁰C) and mild lymphadenopathy. On physical examination, he is irritable, dome-shaped, grouped vesicles with erythematous base present on his forehead, cheeks and left hand, as shown in the image. Vesicles also are scattered on his upper truck and back. Based on the patient's history and physical exam,