Allergy, unspecified, subsequent encounter

This code signifies an allergic reaction of an unknown or unspecific type that is being addressed in a follow-up visit. The patient is experiencing symptoms related to an allergy, but the specific allergen or the precise nature of the allergic response has not been identified or documented.

Use this code for subsequent encounters where a patient is being treated or monitored for an unspecified allergy. This includes visits for ongoing management of symptoms, further diagnostic workup, or evaluation of treatment effectiveness, when the initial diagnosis of "allergy, unspecified" was made.

• Only use for subsequent encounters; an initial encounter would use T78.40XA.
• Strive for greater specificity if the allergen or type of allergy is identified (e.g., food allergy, drug allergy, allergic rhinitis).
• Always review the medical record for documentation that supports the "unspecified" nature of the allergy and the "subsequent encounter" status.