This is the CodeSystem that contains all the codes in AllergyIntoleranceCertainty (http://terminology.hl7.org/CodeSystem/reaction-event-certainty) and AllergyIntoleranceCertainty (http://terminology.hl7.org/CodeSystem/reaction-event-certainty). E.g. what you have to deal with if you get resources containing codes in either of them
Generated Narrative: CodeSystem d90c6776-070a-4707-b535-0a35f2e2298a-1499
This code system http://hl7.org/fhir/comparison/CodeSystem/d90c6776-070a-4707-b535-0a35f2e2298a-1499 defines codes, but no codes are represented here