Version 2024

2024 ICD-10-CM Diagnosis Code T78.40XA

Allergy, unspecified, initial encounter

ICD-10-CM Code:: T78.40XA
ICD-10 Code for:: Allergy, unspecified, initial encounter
Is Billable?: Yes - Valid for Submission
Chronic Condition Indicator: ^[1]: Not chronic
Code Navigator:

Code Information
Approximate Synonyms
Clinical Classification
Coding Guidelines
Tabular List of Diseases and Injuries
Diagnostic Related Groups Mapping
Convert to ICD-9 Code
Patient Education
Other Codes Used Similar Conditions
Code History

Code Classification

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

T78.40XA is a billable diagnosis code used to specify a medical diagnosis of allergy, unspecified, initial encounter. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2023 through September 30, 2024.

T78.40XA is an initial encounter code, includes a 7th character and should be used while the patient is receiving active treatment for a condition like allergy unspecified. According to ICD-10-CM Guidelines an "initial encounter" doesn't necessarily means "initial visit". The 7th character should be used when the patient is undergoing active treatment regardless if new or different providers saw the patient over the course of a treatment. The appropriate 7th character codes should also be used even if the patient delayed seeking treatment for a condition.

Unspecified diagnosis codes like T78.40XA are acceptable when clinical information is unknown or not available about a particular condition. Although a more specific code is preferable, unspecified codes should be used when such codes most accurately reflect what is known about a patient's condition. Specific diagnosis codes should not be used if not supported by the patient's medical record.

Approximate Synonyms

The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

Acute allergic reaction
Adverse cutaneous reaction to diagnostic procedure
Adverse reaction caused by detergent
Adverse reaction to bone resorption inhibitor
Adverse reaction to oil
Allergic bronchitis
Allergic condition
Allergic cough
Allergic disorder
Allergic disorder - symptom change
Allergic disorder monitoring status
Allergic disorder of digestive system
Allergic disorder of respiratory system
Allergic disorder of respiratory tract
Allergic disorder treatment started
Allergic disposition
Allergic encephalitis
Allergic facies
Allergic gingival disease
Allergic otitis externa
Allergic reaction
Allergic reaction after allergen immunotherapy
Allergic reaction caused by analgesic
Allergic reaction caused by anesthetic
Allergic reaction caused by Hevea brasiliensis latex protein
Allergic reaction caused by hymenoptera venom
Allergic reaction caused by hymenoptera venom
Allergic reaction caused by insect bite and/or insect sting
Allergic reaction caused by insect bite and/or insect sting
Allergic reaction caused by insect bite and/or insect sting
Allergic reaction due to allergy skin test
Allergic reaction to adhesive
Allergic reaction to bee sting
Allergic reaction to colophony
Allergic reaction to detergent
Allergic reaction to drug
Allergic reaction to hair dye
Allergic reaction to nickel
Allergic reaction to oil
Allergic reaction to platinum
Allergic reaction to venom
Allergic reaction to wasp sting
Allergic sensitization
Allergic vaginitis
Allergy skin test positive
Allergy test positive
Allergy treatment changed
Allopurinol adverse reaction
Allopurinol hypersensitivity syndrome
Angry back syndrome
Atopic reaction
Cell-mediated immune reaction
Chronic allergic otitis externa
Chronic non-infective otitis externa
Complication of diagnostic procedure
Complication of patch testing
Contact hypersensitivity reaction
Contact hypersensitivity reaction
Cutaneous hypersensitivity
Cutaneous hypersensitivity reaction caused by Hymenoptera venom
Cutis laxa following hypersensitivity reaction
Cutis laxa, acquired type
Drug reaction with eosinophilia and systemic symptoms
Drug reaction with eosinophilia and systemic symptoms
Drug reaction with eosinophilia and systemic symptoms
Drug reaction with eosinophilia and systemic symptoms caused by strontium ranelate
Emollient adverse reaction
Hypersensitivity condition
Hypersensitivity disorder of respiratory tract
Hypersensitivity disposition
Hypersensitivity finding
Hypersensitivity finding
Hypersensitivity finding
Hypersensitivity gingivitis
Hypersensitivity reaction
Hypersensitivity reaction mediated by antibody
Hypersensitivity reaction mediated by immune complex
Hypersensitivity reaction with blocking antibody
Hypersensitivity reaction without blocking antibody
Immune hypersensitivity reaction by mechanism
Injection site hypersensitivity
Laryngotracheobronchitis
Late effect of accidental injury
Late effect of accidental injury
Myocarditis due to hypersensitivity state
Non-allergic hypersensitivity condition
Pain provoked by allergen
Recurrent allergic croup
Recurrent croup
Skin: type 3 delayed reaction
Type 1 hypersensitivity response
Type 1 skin hypersensitivity reaction
Type 4 hypersensitivity response
Ulcer of esophagus due to allergic disorder
Xanthine oxidase inhibitor adverse reaction

Clinical Classification

Clinical Category is Allergic reactions
CCSR Category Code: INJ031
Inpatient Default CCSR: Y - Yes, default inpatient assignment for principal diagnosis or first-listed diagnosis.
Outpatient Default CCSR: Y - Yes, default outpatient assignment for principal diagnosis or first-listed diagnosis.

Coding Guidelines

The appropriate 7th character is to be added to each code from block Adverse effects, not elsewhere classified (T78). Use the following options for the aplicable episode of care:

A - initial encounter
D - subsequent encounter
S - sequela

T78.40XA is grouped with Diagnostic Related Groups - MS-DRG Mapping

Diagnostic Related Groups (DRGs) are a classification system used to group together diagnosis codes for the purpose of reimbursement and healthcare management. DRGs are used to standardize the way hospitals and other providers are paid for inpatient services. In this system patients are grouped together based on their principal diagnosis in areas referred to as Major Diagnostic Categories (MDC). Once a patient is assigned a particular diagnostic category, providers receive a predetermined payment rate for the services rendered. This reimbursement rate is often fixed and is meant to cover the cost of care for that patient. Reimbursement is also affected by the relative weight of a diagnostic related group based on the severity of a patient's illness and the associated cost of care during hospitalization.

Diagnostic related groups encourage healthcare providers to focus on quality and efficiency in patient care while managing costs effectively. The diagnosis code is present in the following groups for version MS-DRG V41.0 applicable from 10/01/2023 through 09/30/2024.

MS-DRG	MS-DRG Title	MCD	Relative Weight
915	ALLERGIC REACTIONS WITH MCC	21	1.774
916	ALLERGIC REACTIONS WITHOUT MCC	21	0.6588

The relative weight of a diagnostic related group determines the reimbursement rate based on the severity of a patient's illness and the associated cost of care during hospitalization.

Convert T78.40XA to ICD-9-CM

ICD-9-CM Code: 995.3 - Allergy, unspecified
Approximate Flag - The approximate mapping means there is not an exact match between the ICD-10 and ICD-9 codes and the mapped code is not a precise representation of the original code.

Patient Education

Allergy

An allergy is a reaction by 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

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. Genes and the environment probably both play a role.

Allergies can cause a variety of symptoms such as a runny nose, sneezing, itching, rashes, swelling, or asthma. Allergies can range from minor to severe. Anaphylaxis is a severe reaction that can be life-threatening. Doctors use skin and blood tests to diagnose allergies. Treatments include medicines, allergy shots, and avoiding the substances that cause the reactions.

[Learn More in MedlinePlus]

Other ICD-10-CM Codes Commonly Used for Similar Conditions

Filter related codes list:

T78 Adverse effects, not elsewhere classified.
T78.0 Anaphylactic reaction due to food.
T78.00 Anaphylactic reaction due to unspecified food.
T78.00XA Anaphylactic reaction due to unspecified food, initial encounter.
T78.00XD Anaphylactic reaction due to unspecified food, subsequent encounter.
T78.00XS Anaphylactic reaction due to unspecified food, sequela.
T78.01 Anaphylactic reaction due to peanuts.
T78.01XA Anaphylactic reaction due to peanuts, initial encounter.
T78.01XD Anaphylactic reaction due to peanuts, subsequent encounter.
T78.01XS Anaphylactic reaction due to peanuts, sequela.
T78.02 Anaphylactic reaction due to shellfish (crustaceans).
T78.02XA Anaphylactic reaction due to shellfish (crustaceans), initial encounter.
T78.02XD Anaphylactic reaction due to shellfish (crustaceans), subsequent encounter.
T78.02XS Anaphylactic reaction due to shellfish (crustaceans), sequela.
T78.03 Anaphylactic reaction due to other fish.
T78.03XA Anaphylactic reaction due to other fish, initial encounter.
T78.03XD Anaphylactic reaction due to other fish, subsequent encounter.
T78.03XS Anaphylactic reaction due to other fish, sequela.
T78.04 Anaphylactic reaction due to fruits and vegetables.
T78.04XA Anaphylactic reaction due to fruits and vegetables, initial encounter.
T78.04XD Anaphylactic reaction due to fruits and vegetables, subsequent encounter.
T78.04XS Anaphylactic reaction due to fruits and vegetables, sequela.
T78.05 Anaphylactic reaction due to tree nuts and seeds.
T78.05XA Anaphylactic reaction due to tree nuts and seeds, initial encounter.
T78.05XD Anaphylactic reaction due to tree nuts and seeds, subsequent encounter.
T78.05XS Anaphylactic reaction due to tree nuts and seeds, sequela.
T78.06 Anaphylactic reaction due to food additives.
T78.06XA Anaphylactic reaction due to food additives, initial encounter.
T78.06XD Anaphylactic reaction due to food additives, subsequent encounter.
T78.06XS Anaphylactic reaction due to food additives, sequela.
T78.07 Anaphylactic reaction due to milk and dairy products.
T78.07XA Anaphylactic reaction due to milk and dairy products, initial encounter.
T78.07XD Anaphylactic reaction due to milk and dairy products, subsequent encounter.
T78.07XS Anaphylactic reaction due to milk and dairy products, sequela.
T78.08 Anaphylactic reaction due to eggs.
T78.08XA Anaphylactic reaction due to eggs, initial encounter.
T78.08XD Anaphylactic reaction due to eggs, subsequent encounter.
T78.08XS Anaphylactic reaction due to eggs, sequela.
T78.09 Anaphylactic reaction due to other food products.
T78.09XA Anaphylactic reaction due to other food products, initial encounter.
T78.09XD Anaphylactic reaction due to other food products, subsequent encounter.
T78.09XS Anaphylactic reaction due to other food products, sequela.
T78.1 Other adverse food reactions, not elsewhere classified.
T78.1XXA Other adverse food reactions, not elsewhere classified, initial encounter.
T78.1XXD Other adverse food reactions, not elsewhere classified, subsequent encounter.
T78.1XXS Other adverse food reactions, not elsewhere classified, sequela.
T78.2 Anaphylactic shock, unspecified.
T78.2XXA Anaphylactic shock, unspecified, initial encounter.
T78.2XXD Anaphylactic shock, unspecified, subsequent encounter.
T78.2XXS Anaphylactic shock, unspecified, sequela.
T78.3 Angioneurotic edema.

Code History

FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.