T78.03XS Anaphylactic reaction due to other fish, sequela

ICD-10-CM T78.03XS: Anaphylactic reaction due to other fish, sequela

ICD-10-CM code T78.03XS identifies a sequela of an anaphylactic reaction caused by other fish. The active terminology record classifies this concept under the parent code T78.03. Public sources confirm the official label and semantic type, while clinical literature provides general context on fish and shellfish allergy mechanisms. 1 2 4

Plain-language overview

Code T78.03XS is an active ICD-10-CM terminology concept representing a sequela of an anaphylactic reaction due to other fish, providing a standardized label for this specific diagnosis. 1

What this code represents

The official preferred name for T78.03XS is Anaphylactic reaction due to other fish, sequela, and the concept is assigned the semantic type Injury or Poisoning in the terminology system. 1 4

T78.03XS has a parent concept, T78.03, which is the broader ICD-10-CM code for an anaphylactic reaction due to other fish, and the target code itself has narrower concepts within the terminology. 1

Clinical context

Clinical literature notes that fish and shellfish combined are suspected to be responsible for a significant portion of allergic reactions, which can range from mild cutaneous symptoms to severe systemic reactions including anaphylaxis. 2

Reactions to shellfish may result from immunologic or nonimmunologic mechanisms, and some reactions are not true allergies but are due to infectious agents such as parasites, bacteria, and viruses. 2

Coverage and utilization context

A Medicare billing and coding article for allergy testing includes T78.03XS in a list of anaphylactic reaction codes, distinguishing it from other food-specific codes like T78.04XA for fruits and vegetables. 3

What the sources add

The National Cancer Institute terminology record and the EVS Explore portal both establish the official label and semantic type for T78.03XS, while the CMS article demonstrates the code's appearance in payer billing contexts. 1 3 4

The clinical literature source provides general background on fish and shellfish allergy mechanisms, whereas the terminology sources define the specific code structure and hierarchical parent for T78.03XS. 1 2 4

Documentation considerations

A Medicare billing and coding article lists T78.03XS alongside other anaphylactic reaction codes with different encounter characters, such as T78.04XA for an initial encounter. 3

Sources

1. ICD-10-CM T78.03XS terminology record — National Cancer Institute Enterprise Vocabulary Services; accessed 2026-07-27.
2. Bookshelf — ncbi.nlm.nih.gov; accessed 2026-07-27.
3. Article - Billing and Coding: Allergy Testing (A57531) — cms.gov; accessed 2026-07-27.
4. EVS Explore — evsexplore.semantics.cancer.gov; accessed 2026-07-27.