2022 ICD-10-CM Diagnosis Code T78.40

Allergy, unspecified

    2016 2017 2018 2019 2020 2021 2022 Non-Billable/Non-Specific Code
  • T78.40 should not be used for reimbursement purposes as there are multiple codes below it that contain a greater level of detail.
  • The 2022 edition of ICD-10-CM T78.40 became effective on October 1, 2021.
  • This is the American ICD-10-CM version of T78.40 - other international versions of ICD-10 T78.40 may differ.
Applicable To
  • Allergic reaction NOS
  • Hypersensitivity NOS
The following code(s) above T78.40 contain annotation back-references
Annotation Back-References
In this context, annotation back-references refer to codes that contain:
  • Applicable To annotations, or
  • Code Also annotations, or
  • Code First annotations, or
  • Excludes1 annotations, or
  • Excludes2 annotations, or
  • Includes annotations, or
  • Note annotations, or
  • Use Additional annotations
that may be applicable to T78.40:
  • S00-T88
    2022 ICD-10-CM Range S00-T88

    Injury, poisoning and certain other consequences of external causes

    Note
    • 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
    Type 1 Excludes
    Use Additional
    • code to identify any retained foreign body, if applicable (Z18.-)
    Injury, poisoning and certain other consequences of external causes
  • T78
    ICD-10-CM Diagnosis Code T78

    Adverse effects, not elsewhere classified

      2016 2017 2018 2019 2020 2021 2022 Non-Billable/Non-Specific Code
    Type 2 Excludes
    • complications of surgical and medical care NEC (T80-T88)
    Adverse effects, not elsewhere classified
  • T78.4
    ICD-10-CM Diagnosis Code T78.4

    Other and unspecified allergy

      2016 2017 2018 2019 2020 2021 2022 Non-Billable/Non-Specific Code
    Type 1 Excludes
    • specified types of allergic reaction such as:
    • allergic diarrhea (K52.29)
    • allergic gastroenteritis and colitis (K52.29)
    • dermatitis (L23-L25, L27.-)
    • food protein-induced enterocolitis syndrome (K52.21)
    • food protein-induced enteropathy (K52.22)
    • hay fever (J30.1)
    Other and unspecified allergy
Clinical Information
  • A disorder characterized by an adverse local or general response from exposure to an allergen.
  • A local or general reaction of an organism following contact with a specific allergen to which it has been previously exposed and to which it has become sensitized.
  • Altered reactivity to an antigen, which can result in pathologic reactions upon subsequent exposure to that particular antigen.
  • An allergy is a reaction of your immune system to something that does not bother most other people. People who have allergies often are sensitive to more than one thing. Substances that often cause reactions are
    • pollen
    • dust mites
    • mold spores
    • pet dander
    • food
    • insect stings
    • medicines
    how do you get allergies? scientists think both genes and the environment have something to do with it. Normally, your immune system fights germs. It is your body's defense system. In most allergic reactions, however, it is responding to a false alarm.allergies can cause a runny nose, sneezing, itching, rashes, swelling or asthma. Symptoms vary. Although allergies can make you feel bad, they usually won't kill you. However, a severe reaction called anaphylaxis is life-threatening.
  • An exaggerated response by the immune system to a drug or other substance.
  • An inflammatory response to an exogenous environmental antigen or an endogenous antigen initiated by the adaptive immune system. [goc:jal, isbn:0781735149]
  • Functions of the body's response of increased sensitization to foreign substances, such as in sensitivities to different antigens.
  • Hypersensitivity to an agent caused by an immunologic response to an initial exposure
  • Hypersensitivity; a local or general reaction of an organism following contact with a specific allergen to which it has been previously exposed and to which it has become sensitized.
  • Known to have allergic reactions to particular substance(s)
  • State of previously immunized body in which tissue damage results from the immune response to a further dose of antigen.
Code History
  • 2016 (effective 10/1/2015): New code (first year of non-draft ICD-10-CM)
  • 2017 (effective 10/1/2016): No change
  • 2018 (effective 10/1/2017): No change
  • 2019 (effective 10/1/2018): No change
  • 2020 (effective 10/1/2019): No change
  • 2021 (effective 10/1/2020): No change
  • 2022 (effective 10/1/2021): No change
Code annotations containing back-references to T78.40:
  • Type 1 Excludes: L23
    , L24
    , L25
    , L27
    ICD-10-CM Diagnosis Code L23

    Allergic contact dermatitis

      2016 2017 2018 2019 2020 2021 2022 Non-Billable/Non-Specific Code
    Type 1 Excludes
    Type 2 Excludes
    • dermatitis due to substances taken internally (L27.-)
    • dermatitis of eyelid (H01.1-)
    • diaper dermatitis (L22)
    • eczema of external ear (H60.5-)
    • irritant contact dermatitis (L24.-)
    • perioral dermatitis (L71.0)
    • radiation-related disorders of the skin and subcutaneous tissue (L55-L59)
    ICD-10-CM Diagnosis Code L24

    Irritant contact dermatitis

      2016 2017 2018 2019 2020 2021 2022 Non-Billable/Non-Specific Code
    Type 1 Excludes
    Type 2 Excludes
    • allergic contact dermatitis (L23.-)
    • dermatitis due to substances taken internally (L27.-)
    • dermatitis of eyelid (H01.1-)
    • diaper dermatitis (L22)
    • eczema of external ear (H60.5-)
    • perioral dermatitis (L71.0)
    • radiation-related disorders of the skin and subcutaneous tissue (L55-L59)
    ICD-10-CM Diagnosis Code L25

    Unspecified contact dermatitis

      2016 2017 2018 2019 2020 2021 2022 Non-Billable/Non-Specific Code
    Type 1 Excludes
    • allergic contact dermatitis (L23.-)
    • allergy NOS (T78.40)
    • dermatitis NOS (L30.9)
    • irritant contact dermatitis (L24.-)
    Type 2 Excludes
    • dermatitis due to ingested substances (L27.-)
    • dermatitis of eyelid (H01.1-)
    • eczema of external ear (H60.5-)
    • perioral dermatitis (L71.0)
    • radiation-related disorders of the skin and subcutaneous tissue (L55-L59)
    ICD-10-CM Diagnosis Code L27

    Dermatitis due to substances taken internally

      2016 2017 2018 2019 2020 2021 2022 Non-Billable/Non-Specific Code
    Type 1 Excludes
    Type 2 Excludes
    • adverse food reaction, except dermatitis (T78.0-T78.1)
    • contact dermatitis (L23-L25)
    • drug photoallergic response (L56.1)
    • drug phototoxic response (L56.0)
    • urticaria (L50.-)

Diagnosis Index entries containing back-references to T78.40:

ICD-10-CM Codes Adjacent To T78.40
T78.1XXS …… sequela
T78.2 Anaphylactic shock, unspecified
T78.2XXA …… initial encounter
T78.2XXD …… subsequent encounter
T78.2XXS …… sequela
T78.3 Angioneurotic edema
T78.3XXA …… initial encounter
T78.3XXD …… subsequent encounter
T78.3XXS …… sequela
T78.4 Other and unspecified allergy
T78.40 Allergy, unspecified
T78.40XA …… initial encounter
T78.40XD …… subsequent encounter
T78.40XS …… sequela
T78.41 Arthus phenomenon
T78.41XA …… initial encounter
T78.41XD …… subsequent encounter
T78.41XS …… sequela
T78.49 Other allergy
T78.49XA …… initial encounter
T78.49XD …… subsequent encounter

Reimbursement claims with a date of service on or after October 1, 2015 require the use of ICD-10-CM codes.