We report a case of a two-year-old boy with atopic dermatitis treated with antibiotics for pharyngitis and acute otitis media and subsequently developed targetoid and ulcerated blister mucocutaneous lesions. Diagnostic workup revealed eczema herpeticum and HSV viremia. To our knowledge, this is the first reported case of a patient with atopic dermatitis presenting with erythema multiforme likely secondary to eczema herpeticum and HSV viremia.