2027 ICD-10-CM Diagnosis Code T78.00XAAnaphylactic reaction due to unspecified food, initial encounter

ICD-10-CM Codes›S00–T88›T66-T78›T78

ICD-10-CM T78.00XA
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

T78.00XA is a billable ICD-10-CM diagnosis code for anaphylactic reaction due to unspecified food, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 915 through 916. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 14 closely related codes. Coders also document this condition as anaphylaxis caused by ingested food. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Allergic reactions.

Code Identity

ICD-10-CM Code
T78.00XA
Billable Status
Yes — Valid for Submission
Code Describes
Anaphylactic reaction due to unspecified food, initial encounter
Short Description
Anaphylactic reaction due to unspecified food, init encntr
Parent Code
T78.00
Anaphylactic reaction due to unspecified food

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT66-T78Other and unspecified effects of external causes
CategoryT78Adverse effects, not elsewhere classified
This CodeT78.00XAAnaphylactic reaction due to unspecified food, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Anaphylaxis caused by ingested food
  • Exercise anaphylaxis
  • Food anaphylaxis
  • Food-dependent exercise-induced anaphylaxis

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Adverse effects, not elsewhere classified (T78). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to T78.00XA: its own notes plus those printed at T78, block T66-T78, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From T78 Adverse effects, not elsewhere classified applies to 81 codes
  • complications of surgical and medical care NEC (T80-T88)
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • code to identify any retained foreign body, if applicable (Z18.-)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

From Block T66-T78 Other and unspecified effects of external causes applies to 456 codes
  • 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-)

Notes

General instructions on how these codes are used.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

7th Character

Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.

From T78 Adverse effects, not elsewhere classified applies to 81 codes
  • The appropriate 7th character is to be added to each code from category T78
Values for category T78 Encounter: Initial, Subsequent, Sequela
  • Ainitial encounter this code
  • Dsubsequent encounter
  • Ssequela

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name T78.00XA, its category, or a range that includes it.

Excludes1 9

These codes carry an Excludes1 note naming T78.00XA: they are not reported together with it, unless the two conditions are unrelated.

  • R57 Shock, not elsewhere classified
    anaphylactic reaction or shock due to adverse food reaction (T78.0-) names T78.0-, which includes this code
  • T61 Toxic effect of noxious substances eaten as seafood
    anaphylactic reaction or shock due to adverse food reaction (T78.0-) names T78.0-, which includes this code
  • T62 Toxic effect of other noxious substances eaten as food
    anaphylactic shock (reaction) due to adverse food reaction (T78.0-) names T78.0-, which includes this code
  • T75 Other and unspecified effects of other external causes
    adverse effects NEC (T78.-) names T78.-, which includes this code
  • T78.1 Other adverse food reactions, not elsewhere classified
    anaphylactic reaction or shock due to adverse food reaction (T78.0-) names T78.0-, which includes this code
  • T78.1 Other adverse food reactions, not elsewhere classified
    anaphylactic reaction due to food (T78.0-) names T78.0-, which includes this code
  • T78.2 Anaphylactic shock, unspecified
    anaphylactic reaction or shock due to adverse food reaction (T78.0-) names T78.0-, which includes this code
  • T79.4 Traumatic shock
    anaphylactic shock due to adverse food reaction (T78.0-) names T78.0-, which includes this code
  • T88.6 Anaphylactic reaction due to adverse effect of correct drug or medicament properly administered
    anaphylactic shock or reaction due to adverse food reaction (T78.0-) names T78.0-, which includes this code

Excludes2 1

These codes carry an Excludes2 note naming T78.00XA: its condition is not part of those codes, and both may be reported when the patient has both.

  • L27 Dermatitis due to substances taken internally
    adverse food reaction, except dermatitis (T78.0-T78.1) names T78.0-T78.1, which includes this code

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INJ031
Allergic reactions
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Anaphylaxis

Anaphylaxis is a serious allergic reaction. It can begin very quickly, and symptoms may be life-threatening. The most common causes are reactions to foods (especially peanuts), medications, and stinging insects. Other causes include exercise and exposure to latex. Sometimes no cause can be found.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert T78.00XA to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
995.60 Anphylct react food NOS
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About T78.00XAOverview

What is the ICD-10 code for anaphylactic reaction due to unspecified food, initial encounter?

The ICD-10-CM code for anaphylactic reaction due to unspecified food, initial encounter is T78.00XA (sometimes written as T7800XA). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is T78.00XA (Anaphylactic reaction due to unspecified food) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report anaphylactic reaction due to unspecified food, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character A in T78.00XA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for anaphylactic reaction due to unspecified food, such as an emergency visit or first evaluation.

What MS-DRG does T78.00XA group to?

When anaphylactic reaction due to unspecified food, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 915, 916, with relative weights from 0.6926 to 1.6559 depending on complications. Higher weights mean higher Medicare reimbursement.

Is T78.00XA a CC or MCC?

CMS lists T78.00XA as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 14 closely related codes in its exclusion list.