A substance or other type of agent (e.g., sunshine) that may be associated with an intolerance reaction event or a propensity to such an event. These concepts are expected to be at a more general level of abstraction (ingredients versus more specific formulations). This value set is quite general and includes concepts that may never cause an adverse event, particularly the included SNOMED CT concepts. The code system-specific value sets in this grouping value set are intended to provide broad coverage of all kinds of agents, but the expectation for use is that the chosen concept identifier for a substance should be appropriately specific and drawn from the available code systems in the following priority order: 1. NDF-RT codes for drug class allergies 2. RxNorm codes limited to term types (TTY) , 'BN' Brand Name, 'IN' ingredient, 'MIN' multiple ingredient, and 'PIN' precise ingredient for drug ingredient allergies 3. SNOMED CT including concepts from SCTID 716186003 No Known allergy (situation) and if no other code from above code systems are available