The following topic describes information for the AllergyIntolerance resource.

To interact with the REST endpoints in the AllergyIntolerance resource, see AllergyIntolerance.


The AllergyIntolerance resource provides the clinical assessment of a patient's allergy or intolerance when exposed to a specific substance, or class of substance, including information about the adverse reaction. Substances include, but are not limited to, medications, foods, environment (such as plants and animals), and insect bites. The allergy or intolerance list exists as a patient safety tool for clinical decision support when ordering medications and nutrition or guiding clinical treatments. This resource does not include adverse reactions or adverse events that are expected for the circumstance, such as an overdose or drug-drug interaction, or an error in the clinical process. References to implicitRules and modifierExtensions are not supported and fail a create or update request.

No Known Allergies (NKA) and No Known Medication Allergies (NKMA) are conveyed with predefined codes while Not Asked is conveyed through the absence of information (empty query response). Consumers can supply the negation codes (No known allergy (situation))(716186003) or No Known Medication Allergies (409137002) as long as the patient's profile contains no other active allergies. If the patient's profile has other active allergies and the consumer tries to add one of the codes above, the service returns an exception.

If NKA, NKMA, or both exist on the patient's allergy profile and a new allergy is added, the NKA and NKMA statuses are canceled.

If the consumer sends information that is deemed a duplicate (codified or free text), the service updates the existing allergy or reaction rather than adding a duplicate allergy or reaction.

With a patient safety or decision support use case, a consumer should avoid querying by status. The status field is not required and can ignore any entered-in-error allergies or intolerances.

This resource supports the following HL7 FHIR US Core Implementation Guide STU 4.0.0 profile:

The following fields are returned if valued:

Terminology Bindings


All URLs for custom extensions are defined as{id}

Table - Extensions

ID Value[x] Type Description
precision CodeableConcept The indication of the precision of a given value.