Penicillin Allergy Delabeling After a One-Dose Versus Two-Dose Graded Direct Oral Challenge

Inclusion Criteria: * Expresses interest in participating by calling or filling out information form on study website * Reports an allergy to one of the following medications: penicillin VK, penicillin G, amoxicillin, ampicillin, dicloxacillin, flucloxacillin, nafcillin, oxacillin, amoxicillin- clavulanate, ampicillin-sulbactam. Subjects with an unspecified penicillin allergy are also eligible to participate. Exclusion Criteria: * Penicillin allergy deemed to be more than "low-risk" per PEN-FAST (score ≥ 3 points) * History of acute kidney injury (acute interstitial nephritis), severe liver impairment (drug- induced liver injury), serum sickness, or isolated drug fever attributed to a penicillin- based antibiotic * Anaphylaxis for any reason in the last year * Cognitive impairment where a collateral history could not be obtained and/or patient does not have capacity to consent for themselves * Pregnant (self-reported) * Any illness or condition that would increase the risk of participation in the study, per the evaluating clinician's judgment * Active treatment of or history of acute angle closure glaucoma * On H1- or H2-blockers (i.e. diphenhydramine, hydroxyzine, chlorpheniramine, cetirizine, levocetirizine, loratadine, fexofenadine or famotidine, ranitidine, cimetidine, nizatidine, respectively) within 72 hours of initiating direct oral challenge (will be counseled to discontinue prior to testing) * Actively receiving greater than stress dose steroid (hydrocortisone \>50mg four times a day or steroid equivalent) * Actively receiving any antibiotic * Relative contraindication: Patients on beta blockers and angiotensin converting enzyme inhibitors (ACE inhibitors) will have an open dialog with the study team regarding the risks and benefits of testing a low-risk penicillin allergy patient. A joint decision will be made based on the patient's preference and the physician's comfort level.