Penicillin allergy is one of the most frequently self-reported allergies in today’s health care with approximately 10% of patients reporting a penicillin allergy.1 Nevertheless only 1% of the general population are truly affected by Ig-E-mediated allergies and most lose their sensitivity during follow-up.2 Reported penicillin allergies have been shown to be associated with worse patient outcomes. The gene discussed is IGHE; the disease is response to penicillin.