ICD-10-CM › S00-T88 › T66-T78 › T78.40 Allergy, unspecified › T78.40XD

Valid for claims with a date of service in the current code year.

Valid FY2016 onwards.

What has happened to this code

Official coding rules

Published by CDC for FY2027. A rule attached to a category binds every code beneath it, so the rules inherited from this code's ancestors are shown with the code they come from.

Inherited from T78 Adverse effects, not elsewhere classified

Seventh character required

• The appropriate 7th character is to be added to each code from category T78

Excludes2 - not included here

• complications of surgical and medical care NEC (T80-T88)

Inherited from the T66-T78 section Other and unspecified effects of external causes (T66-T78)

Code also

• , if applicable, place of occurrence, such as:
• highway rest stop (Y92.523)
• school (private) (public) (state) as the place of occurrence of the external cause (Y92.21-)
• service areas as the place of occurrence of the external cause (Y92.52-)
• single-family non-institutional (private) house as the place of occurrence of the external cause (Y92.01-)
• transport vehicle as the place of occurrence of the external cause (Y92.81-)

How CDC's index refers to this code

Wording from the official alphabetic index. Much of it appears nowhere in the code description, which is why a search for the everyday phrase so often finds nothing.

• Disorder > allergic
• Hypersusceptibility
• Reaction > allergic
• Sensitive, sensitivity
• Allergy, allergic > medicine
• Allergy, allergic > biological
• Reaction > drug NEC > allergic
• Complication > injection > drug reaction
• Hypersensitive, hypersensitiveness, hypersensitivity
• Allergy, allergic
• Allergy, allergic > drug, medicament & biological
• Hypersensitive, hypersensitiveness, hypersensitivity > reaction

Codes in the same group

Code	Description	Status
T78.40XA	Allergy, unspecified, initial encounter	Valid
T78.40XS	Allergy, unspecified, sequela	Valid