A computerized prescriber order entry (CPOE) system provides an additional alert about possible allergic reactions a patient might have to a prescribed medication. The patient’s allergy information should be linked to the ordering system, so that if a prescriber selects a medication to which the patient has a known or related allergy, an alert will show up on the screen. The alert gives the prescriber the opportunity to alter the selection during the ordering process and avoid an error or adverse drug event.