IGHE and response to penicillin: Penicillin allergy is one of the most commonly reported antibiotic allergies globally, with 10% of adults reporting penicillin allergies in the USA.1 However, clinically significant IgE-mediated or T lymphocyte-mediated penicillin hypersensitivity is rare, with a reported prevalence of less than 5%.1 A Singapore study found that 85.8% of patients who reported a β-lactam allergy were found not to be allergic on specific testing.2