> ## Documentation Index
> Fetch the complete documentation index at: https://docs.connectivehealth.io/llms.txt
> Use this file to discover all available pages before exploring further.

# AllergyIntolerance

> The FHIR AllergyIntolerance resource as produced by Connective Health

[FHIR R4 AllergyIntolerance](https://www.hl7.org/fhir/R4/allergyintolerance.html) ·
[US Core AllergyIntolerance](https://hl7.org/fhir/us/core/STU9/StructureDefinition-us-core-allergyintolerance.html)

<Info>
  This resource is produced identically for the [Patient Everything](/fhir/patient-everything-bundle) and
  [Patient Summary](/fhir/patient-summary-bundle) bundles. It is not produced for
  [Bulk Medication History](/fhir/bulk-medication-history-bundle).
</Info>

# Stable ID

The `id` is derived from the patient, the recorded date, the allergen code, and the reaction manifestation code, and
the reaction severity code. If a subsequent bundle contains a record with all the same values, it resolves to the same `AllergyIntolerance`.

# Fields

| Field                    | Cardinality | Notes                                                                                                                                                                                            |
| ------------------------ | ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `meta.profile`           | 1..1        | Always set to the US Core AllergyIntolerance profile URL.                                                                                                                                        |
| `patient`                | 1..1        | Reference to the [Patient](/fhir/resources/patient).                                                                                                                                             |
| `clinicalStatus`         | 1..1        | Currently, always `active` from the [allergyintolerance-clinical](http://terminology.hl7.org/CodeSystem/allergyintolerance-clinical) system.                                                     |
| `verificationStatus`     | 1..1        | Currently, always `unconfirmed` from the [allergyintolerance-verification](http://terminology.hl7.org/CodeSystem/allergyintolerance-verification) system.                                        |
| `code`                   | 1..1        | A single coding for the allergen, from the source allergen code.                                                                                                                                 |
| `reaction`               | 1..1        | Exactly one reaction entry is always produced, even when neither manifestation nor severity is known.                                                                                            |
| `reaction.manifestation` | 1..1        | A single coding for the reaction the patient experienced.                                                                                                                                        |
| `reaction.severity`      | 0..1        | Only populated when the source carries a severity code. Recognized values map straight through to `mild`, `moderate`, or `severe`; **any unrecognized severity value is published as `severe`**. |

<Warning>
  Because an unrecognized severity is reported as `severe`, a `severe` value should not be read as a positive
  clinical assertion of severity on its own.
</Warning>

<Note>
  `onsetDateTime`, `recordedDate`, `criticality`, `type`, and `category` are not populated. The source date is used
  to determine which allergies are the most recent (see
  [Data Limits](/fhir/patient-everything-bundle#data-limits)) and contributes to the stable `id`, but it is not
  published as a field on the resource.
</Note>