T78.4
Other and unspecified allergy
Not billable — category only FY2026 2025-10-01 → 2026-09-30
This is the unspecified option. 5 more
specific codes sit alongside it. Worth
checking whether the documentation supports one of them.
Exclusions 10 never code together
T78.4code
Excludes1
- specified types of allergic reaction such as:
- allergic diarrhea (K52.29)K52.29K52.29
- allergic gastroenteritis and colitis (K52.29)K52.29K52.29
- dermatitis (L23-L25, L27.-)L23-L25L23-L25L27.-L27.-
- food protein-induced enterocolitis syndrome (K52.21)K52.21K52.21
- food protein-induced enteropathy (K52.22)K52.22K52.22
- hay fever (J30.1)J30.1J30.1
Excludes1 — never code together. The excluded condition and this one are mutually exclusive.
Excludes2 — not included here, but the patient may have both. Code both when documented.
7th character 3
A initial encounter
D subsequent encounter
S sequela
Instructional notes 3
S00-T88chapter
Notes
- 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.
Use additional code
- code to identify any retained foreign body, if applicable (Z18.-)Z18.-
Index entries leading here filed at null
No alphabetic index entry points at this code.
Alongside this code 5 same parent — T78
Subordinate codes 3
Additional references
AHA Coding Clinic® Licence required
Official coding advice for this code. Published by the American Hospital Association. Not included in this installation.