2026 ICD-10-CM Diagnosis Code T78.05XAAnaphylactic reaction due to tree nuts and seeds, initial encounter
T78.05XA is a billable ICD-10-CM diagnosis code for anaphylactic reaction due to tree nuts and seeds, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 915 through 916. Coders also document this condition as allergic reaction caused by seed. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Allergic reactions.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Allergic reaction caused by seed
- Allergic reaction caused by tree nut
- Anaphylaxis caused by seed
- Anaphylaxis caused by tree nut
Coding GuidelinesGuidance
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 applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Anaphylaxis
Anaphylaxis is a serious allergic reaction. It can begin very quickly, and symptoms may be life-threatening. The most common causes are reactions to foods (especially peanuts), medications, and stinging insects. Other causes include exercise and exposure to latex. Sometimes no cause can be found.
Read the full article at MedlinePlus
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Convert T78.05XA to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T78.05XAOverview
Is T78.05XA (Anaphylactic reaction due to tree nuts and seeds) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report anaphylactic reaction due to tree nuts and seeds, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T78.05XA mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for anaphylactic reaction due to tree nuts and seeds, such as an emergency visit or first evaluation.
What MS-DRG does T78.05XA group to?
When anaphylactic reaction due to tree nuts and seeds, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 915, 916, with relative weights from 0.6663 to 1.6816 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of T78.05XA?
Under the General Equivalence Mappings, anaphylactic reaction due to tree nuts and seeds, initial encounter converts to ICD-9-CM 995.64 (anphyl react tr nts seed). The mapping is approximate, so confirm the match fits the documentation.
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.
