T78.129A — Other adverse food reaction due to egg with baked egg tolerance/reactivity, unspecified, initial encounter
Is T78.129A billable?
Yes, but T78.129A is an unspecified code. T78.129A is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, T78.129A is an unspecified or catch-all code. Payers apply additional scrutiny to unspecified codes and many deny them when the medical record supports a more specific option, so check the documentation before selecting T78.129A — the more specific alternatives are listed below.
T78.129A at a glance
| Code | T78.129A |
|---|---|
| Description | Other adverse food reaction due to egg with baked egg tolerance/reactivity, unspecified, initial encounter |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
| 7th character "A" | initial encounter |
What does the 7th character "A" mean in T78.129A?
In T78.129A, the 7th character A means initial encounter. The 7th character is required for T78.129A to be a valid, complete code.
Same condition, different episode of care — switch the 7th character:
What Medicare edits apply to T78.129A?
The Medicare Code Editor screens inpatient claims before they are grouped. These edits name T78.129A directly.
CMS will reject this code as the principal diagnosis on an inpatient claim. It describes something other than the condition chiefly responsible for the admission.
Which MS-DRGs does T78.129A group to?
T78.129A sits in MDC 21 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 922Other Injury, Poisoning and Toxic Effect Diagnoses with MCCmedical
- 923Other Injury, Poisoning and Toxic Effect Diagnoses without MCCmedical
How is T78.129A listed in the Alphabetic Index?
The Alphabetic Index lists these routes under T78.129, the nearest indexed parent of T78.129A. Use them to find the family, then select the specific code.
- Allergy, allergic › eggs › adverse reaction NEC (reaction) (to)
Excludes1 — never code together — inherited from T78.1
The conditions below can never be reported together with T78.129A on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Use additional code — inherited from Chapter 19
Report an additional code alongside T78.129A to fully describe the condition. T78.129A is sequenced first.
- code to identify any retained foreign body, if applicable (Z18.-)
Use additional code — inherited from T78.1
Report an additional code alongside T78.129A to fully describe the condition. T78.129A is sequenced first.
- code to identify the type of reaction, if applicable
Excludes2 — not included here — inherited from Chapter 19
The conditions below are not part of T78.129A, but a patient may have both at the same time. When documentation supports it, T78.129A and the excluded code may both be reported.
Excludes2 — not included here — inherited from T78
The conditions below are not part of T78.129A, but a patient may have both at the same time. When documentation supports it, T78.129A and the excluded code may both be reported.
- complications of surgical and medical care NEC (T80-T88)
Excludes2 — not included here — inherited from T78.1
The conditions below are not part of T78.129A, but a patient may have both at the same time. When documentation supports it, T78.129A and the excluded code may both be reported.
Code also — inherited from T66-T78
Two codes may be needed to describe the condition fully. Whether T78.129A is sequenced first depends on the reason for the encounter.
- , if applicable, place of occurrence, such as:
- highway rest stop (Y92.523)
- school (private) (public) (state) as the place of occurrence of the external cause (Y92.21-)
- service areas as the place of occurrence of the external cause (Y92.52-)
- single-family non-institutional (private) house as the place of occurrence of the external cause (Y92.01-)
- transport vehicle as the place of occurrence of the external cause (Y92.81-)
How long has T78.129A existed?
T78.129A first appears in FY2026.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.