The Allergy Processor uniquely identifies allergies based on both the HL7 code for the allergy and the assigning authority. HL7 messages do not need to provide assigning authorities for allergies, but the assigning authority will be recorded if provided.
The assigning authority is the value in the third component of the HL7 field containing the Allergy - Allergy1 value. This location is not configurable. If a value is provided in this location, it will be used as the assigning authority for the specified allergy.