L23 vs T78.4
L23 (Allergic contact dermatitis) compared with T78.4 (Other and unspecified allergy), 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. T78.4 carries an Excludes1 note covering L23: “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
| L23Allergic contact dermatitis | T78.4Other and unspecified allergy | |
|---|---|---|
| Billing status | Non-billable header | Non-billable header Report instead: T78.40XA, T78.40XD, T78.40XS, T78.41XA, T78.41XD |
| 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 | Allergic contact dermatitis is a non-billable ICD-10-CM category code (L23). | Other and unspecified allergy is a non-billable ICD-10-CM category code (T78.4). |
| 7th character | — | The appropriate 7th character is to be added to each code from category T78 |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources