Hao M, Zang P, Miller M, et al. - The authors reviewed all recent erythema multiforme (EM), an acute dermatologic condition frequently encountered in the Emergency Department, cases seen at the LAC-USC County Hospital in order to determine the proportion of herpes associated EM (HAEM) cases and to inform the diagnostic workup of these patients. From 2013 to 2019, ICD-9 and ICD-10 codes were used to extract a list of EM cases at the institution. The sample consisted of 70 pediatric and 56 adult EM patients. In most EM patients, HSV-1/2 serologic testing should be considered to potentially prevent repeated ED visits. In EM cases that are not clearly attributable to herpes or drug exposure, doctors may consider further workup: Mycoplasma serology, nasal PCR, and a respiratory viral panel in pediatric patients. Identification of the etiologic cause may suggest a different approach to treatment and prevent mislabeling of drug allergies in patient charts.