ICD-10 Code
International Classification of Diseases, 10th Revision
Oct 21, 2018

See: Other and unspecified allergy

  ICD-10 Code for Allergy, unspecified T78.40

T78.40 is a valid1 ICD 10 diagnosis code.

T78.40 is NOT valid for submission for HIPAA-covered transactions.

Chapter 19 Injury, poisoning and certain other consequences of external causes (S00-T88)
Section T66-T78 Other and unspecified effects of external causes (T66-T78)
Category T78 Adverse effects, not elsewhere classified

• See below for any additional coding requirements that may be necessary.

• Check for any notations, inclusions and/or exclusions that are specific to this ICD 10 code before using

1 The appropriate 7th character is to be added along with any placeholders (X) necessary to establish a 7-digit ICD 10 code.
  • T78.40XA - Allergy, unspecified
    Use this code for initial encounter
  • T78.40XD - Allergy, unspecified
    Use this code for subsequent encounter
  • T78.40XS - Allergy, unspecified
    Use this code for sequela
Inclusion Term
  • Allergic reaction NOS
  • Hypersensitivity NOS
See also ICD 10 code for

Related Terms to “Allergy, unspecified”

  • Allergy, allergic(reaction) (to) - T78.40
    • drug, medicament & biological(any) (external) (internal) - T78.40
  • Hypersensitive, hypersensitiveness, hypersensitivitySee also Allergy
    • reaction - T78.40
See the ICD-10-CM Coding Guidelines.

Questions related to T78.40 Allergy, unspecified

When ICD 10 was implemented on October 1, 2015, it did not affect physicians', outpatient facilities', and hospital outpatient departments' use of CPT codes on Medicare Fee-For-Service claims. Providers should continue to use CPT codes to report these services.