This code system http://hl7.org/fhir/allerg-intol-substance-exp-risk defines the following codes:

CodeDisplayDefinition
known-reaction-riskKnown Reaction RiskKnown risk of allergy or intolerance reaction upon exposure to the specified substance.
no-known-reaction-riskNo Known Reaction RiskNo known risk of allergy or intolerance reaction upon exposure to the specified substance.