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

Billable ICD-10-CM code, FY2026.

Built from T78.121 with 7th character S (sequela).

Applies from T78 Adverse effects, not elsewhere classified

Excludes2 (not included here)

• complications of surgical and medical care NEC (T80-T88)

7th character note

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

7th character required

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

Applies from T78.1 Other adverse food reactions, not elsewhere classified

Excludes1 (never code together)

• anaphylactic reaction or shock due to adverse food reaction (T78.0-)
• anaphylactic reaction due to food (T78.0-)
• bacterial food borne intoxications (A05.-)

Excludes2 (not included here)

• 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

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

Excludes1 (never code together)

• Other adverse food reaction due to egg with tolerance to baked egg (T78.120)

Medicare Code Edits (MCE v43.1 (April 2026))

• Unacceptable principal diagnosis: These codes describe a circumstance which influences care but is not a current illness or injury, or capture only an underlying condition, and are unacceptable as principal diagnosis.

Code annotations containing back-references to T78.121S

Back-references to T78.121

• Type 1 Excludes: T78.120 Other adverse food reaction due to egg with tolerance to baked egg ("Other adverse food reaction due to egg with reactivity to baked egg (T78.121)")

Back-references to T78.1

• Type 2 Excludes: L27 Dermatitis due to substances taken internally ("adverse food reaction, except dermatitis (T78.0-T78.1)")

Back-references to T78

• Type 1 Excludes: T75 Other and unspecified effects of other external causes ("adverse effects NEC (T78.-)")

Diagnosis Index entries for T78.121S

• Allergy, allergic (reaction) (to) › eggs › adverse reaction NEC › with › reactivity to baked egg

Nearby codes

• T78.120D Other adverse food reaction due to egg with tolerance to baked egg, subsequent encounter
• T78.120S Other adverse food reaction due to egg with tolerance to baked egg, sequela
• T78.121 Other adverse food reaction due to egg with reactivity to baked egg
• T78.121A Other adverse food reaction due to egg with reactivity to baked egg, initial encounter
• T78.121D Other adverse food reaction due to egg with reactivity to baked egg, subsequent encounter
• T78.121S Other adverse food reaction due to egg with reactivity to baked egg, sequela (this code)
• T78.129 Other adverse food reaction due to egg with baked egg tolerance/reactivity, unspecified
• T78.129A Other adverse food reaction due to egg with baked egg tolerance/reactivity, unspecified, initial encounter
• T78.129D Other adverse food reaction due to egg with baked egg tolerance/reactivity, unspecified, subsequent encounter
• T78.129S Other adverse food reaction due to egg with baked egg tolerance/reactivity, unspecified, sequela
• T78.19 Other adverse food reactions, not elsewhere classified