2027 ICD-10-CM Diagnosis Code Z91.0120Allergy to eggs, unspecified
Z91.0120 is a billable ICD-10-CM diagnosis code for allergy to eggs, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 951. The code is not accepted as a principal diagnosis by the Medicare Code Editor and exempt from POA reporting. Coders also document this condition as allergy to egg protein. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified status.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for Z91.0120.
Present on Admission (POA)Billing
Z91.0120 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review the other POA exempt codes in Persons with potential health hazards related to family and personal history and certain conditions influencing health status (Z77-Z99).
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Allergy to egg protein
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to Z91.0120: its own notes plus those printed at Z91.01, Z91.0, Z91, block Z77-Z99, and Chapter 21. A note printed at a category, block or chapter applies to every code under it.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- Allergy status to drugs, medicaments, and biological substances (Z88.-)
Code Also
A second code may be needed to fully describe the condition; the note gives no sequencing direction.
Notes
General instructions on how these codes are used.
- Z codes represent reasons for encounters. A corresponding procedure code must accompany a Z code if a procedure is performed. Categories Z00-Z99 are provided for occasions when circumstances other than a disease, injury or external cause classifiable to categories A00-Y89 are recorded as 'diagnoses' or 'problems'. This can arise in two main ways:
- (a) When a person who may or may not be sick encounters the health services for some specific purpose, such as to receive limited care or service for a current condition, to donate an organ or tissue, to receive prophylactic vaccination (immunization), or to discuss a problem which is in itself not a disease or injury.
- (b) When some circumstance or problem is present which influences the person's health status but is not in itself a current illness or injury.
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name Z91.0120, its category, or a range that includes it.
Excludes2 1
These codes carry an Excludes2 note naming Z91.0120: its condition is not part of those codes, and both may be reported when the patient has both.
Use Additional Code 2
These codes say to use an additional code from the note, and Z91.0120 is one of the codes named.
Index to Diseases and InjuriesGuidance
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Food Allergy
A food allergy is an abnormal immune system reaction to certain foods. Your immune system normally protects you from germs. But if you have a food allergy, your immune system mistakenly reacts to certain foods as if they were harmful. This reaction is usually mild. But in some cases, it can be serious or even life-threatening.
The full article covers:
- What is a food allergy?
- Who is more likely to develop a food allergy?
- What are the symptoms of food allergies?
- How are food allergies diagnosed?
- What are the treatments for food allergies?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Code History & ChangesHistory
Replacement Z91.0120 replaces the following previously assigned code(s):
- Z91.012 - Allergy to eggs
Questions About Z91.0120Overview
What is the ICD-10 code for allergy to eggs, unspecified?
The ICD-10-CM code for allergy to eggs, unspecified is Z91.0120 (sometimes written as Z910120). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is Z91.0120 (Allergy to eggs) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report allergy to eggs, unspecified on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does Z91.0120 group to?
On inpatient claims, allergy to eggs, unspecified maps to MS-DRG 951 (other Factors Influencing Health Status), which carries a relative weight of 0.5574. Higher weights mean higher Medicare reimbursement.
Can Z91.0120 be a principal diagnosis?
No. The Medicare Code Editor rejects this code as a principal diagnosis because allergy to eggs, unspecified describes a circumstance that influences health status rather than a current illness. Report it as a secondary diagnosis.
Is Z91.0120 exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for allergy to eggs, unspecified on inpatient claims. The code appears in the Persons with potential health hazards related to family and personal history and certain conditions influencing health status (Z77-Z99) range of the CMS exempt list.
