T78.40: Allergy, unspecified
T78.40 is a non-billable header ICD-10-CM code for allergy, unspecified. It cannot be billed on its own: choose one of the more specific child codes below. This code also requires a 7th character before it is complete.
This code requires a 7th character
The appropriate 7th character is to be added to each code from category T78
- A
- initial encounter
- D
- subsequent encounter
- S
- sequela
Inclusion terms
Alternative wordings a physician may use in the chart for this same code.
- Allergic reaction NOS
- Hypersensitivity NOS
Excludes1 inherited from the categories above T78.40
A category’s note binds every code beneath it.
Written on T78.4: Other and unspecified allergy
Excludes2 inherited from the categories above T78.40
Not part of this code, but both may be coded when both are present.
Other codes that can never be billed with T78.40
Their own Excludes1 notes name this code, so the conflict is not listed above.
Risk adjustment
No CMS-HCC V28 category: this code does not change a RAF score.
Alphabetic index entries that lead here
- Allergy, allergic(reaction) (to)
- Allergy, allergic›drug, medicament & biological(any) (external) (internal)
- Hypersensitive, hypersensitiveness, hypersensitivity›reaction
Code history
Unchanged in every release from FY2024 to FY2027.
Code to one of these instead T78.40
3 child codes. Green means billable.