Adverse drug events (ADEs) are critical. Approximately 10% of fatal ADEs are believed to be allergic reactions. Therefore, sharing patient allergy information is beneficial to medical staff members in avoiding potentially lethal complications. We previously performed a nationwide study of patient allergy information in Japanese hospitals. The report showed that most of the responding hospitals needed a standard format for reporting the information. To establish this, we implemented a novel format for recording patient allergy information into the hospital information system at Tohoku University Hospital; this format was created through vigorous discussion among medical staff members with a variety of specialties, including doctors, nurses, pharmacists, nutritionists, and medical safety managers. In this study, we followed the amount of inputted allergy information and the number of incidents involving medication after implementation. The amount of allergy information inputted increased slightly. Although incidents involving medication also increased slightly, ADEs due to allergy significantly decreased. We believe that our findings will be useful in helping to determine the optimal characteristics of drug allergy information and to improve the dissemination of information regarding potential allergens and subsequent ADEs.