L27 vs T78.40
L27 (Dermatitis due to substances taken internally) compared with T78.40 (Allergy, unspecified), from the official CMS tabular data. Do not report these codes together: the official tabular list marks them Excludes1.
Can these codes be reported together?
No — do not report together. L27 carries an Excludes1 note covering T78.40: “allergy NOS (T78.40)”
Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).
No — do not report together. T78.40 carries an Excludes1 note covering L27: “dermatitis (L23-L25, L27.-)”
Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).
Side by side
| L27Dermatitis due to substances taken internally | T78.40Allergy, unspecified | |
|---|---|---|
| Billing status | Non-billable header | Non-billable header |
| Classification | L00-L99 — Diseases of the Skin and Subcutaneous Tissue (L00-L99) | S00-T88 — Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) |
| Definition | Dermatitis due to substances taken internally is a non-billable ICD-10-CM category code (L27). | Allergy, unspecified is a non-billable ICD-10-CM category code (T78.40). |
| 7th character | — | The appropriate 7th character is to be added to each code from category T78 |
| Includes | — | Allergic reaction NOS Hypersensitivity NOS |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources