Penicillin allergy is the most common drug allergy in the world.1,2,3,4,5 Although 5% to 10% of the population is labeled as penicillin allergic,6,7,8,9 more than 95% of children with this allergy label are not found to have a type 1 IgE-mediated hypersensitivity after penicillin skin testing or oral challenge.4,10,11,12,13,14 Unconfirmed penicillin allergy labels (PALs), specific designations in the medical record to signify a history of penicillin allergy, can lead to potentially unnecessary receipt of broad spectrum, second-line antibiotics. Here, IGHE is linked to response to penicillin.