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ICD-10-CM 2027 diagnosis code

T78.121Other adverse food reaction due to egg with reactivity to baked egg

Not billable — use a more specific codeRequires 7th character

T78.121 is a header code, so it can't be reported by itself. Choose one of the 3 more specific codes beneath it and add the required 7th character.Short description: Other adverse food reaction due to egg with rct to baked egg

Code last changed in FY2026 (effective October 1, 2025). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About T78.121

T78.121 is the ICD-10-CM diagnosis code for other adverse food reaction due to egg with reactivity to baked egg. It belongs to category T78 (adverse effects, not elsewhere classified), block T66-T78 (other and unspecified effects of external causes) and chapter 19 (injury, poisoning and certain other consequences of external causes). It is a header code, so it can't be reported by itself; one of its 3 subcodes must be used instead.

Within T78.12 (other adverse food reaction due to eggs), T78.121 is specifically for other adverse food reaction due to egg with reactivity to baked egg. Related codes cover tolerance to baked egg (T78.120) and baked egg tolerance/reactivity, unspecified (T78.129).

Codes in this range require a 7th character: A for initial encounter, D for subsequent encounter and S for sequela. Use placeholder "X" characters to fill any empty positions before the 7th character.

Don't report T78.121 together with the conditions in its Excludes1 note: Other adverse food reaction due to egg with tolerance to baked egg (T78.120).

It was added in FY2026, effective October 1, 2025.

7th character

The appropriate 7th character is to be added to each code from category T78

Coding notes

Excludes1Not coded here — never report together with this code
  • Other adverse food reaction due to egg with tolerance to baked egg (T78.120)

Notes that apply from higher levels

Instructions written at a parent level also apply to T78.121.

› From T78.1 Other adverse food reactions, not elsewhere classified
Excludes1
  • anaphylactic reaction or shock due to adverse food reaction (T78.0-)
  • anaphylactic reaction due to food (T78.0-)
  • bacterial food borne intoxications (A05.-)
Excludes2
  • allergic and dietetic gastroenteritis and colitis (K52.29)
  • allergic rhinitis due to food (J30.5)
  • dermatitis due to food in contact with skin (L23.6, L24.6, L25.4)
  • dermatitis due to ingested food (L27.2)
  • food protein-induced enterocolitis syndrome (K52.21)
  • food protein-induced enteropathy (K52.22)
Use additional code
  • code to identify the type of reaction, if applicable
› From T78 Adverse effects, not elsewhere classified
Excludes2
  • complications of surgical and medical care NEC (T80-T88)

Broader instructions also apply from T66-T78 Other and unspecified effects of external causes and Chapter 19: Injury, poisoning and certain other consequences of external causes.

Alphabetic index entries

1 entries

Terms in the official ICD-10-CM index that lead to T78.121.

Codes whose notes reference T78.121

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2026 (effective 10/1/2025): Added
  • No changes since FY2026.

Common questions about T78.121

Is T78.121 billable?

No. T78.121 is a header code. Report one of its more specific subcodes instead.