This study will evaluate whether blood tests that measure IgE antibodies to two shrimp proteins, tropomyosin and hemocyanin, can help diagnose shrimp allergy in children. Children with suspected IgE-mediated shrimp allergy will undergo oral food challenge, skin prick testing, and blood sampling. Oral food challenge results will be used as the reference standard to determine whether these tests can accurately identify true shrimp allergy and help improve diagnosis in clinical practice.

Shrimp allergy is an important cause of IgE-mediated food allergy in children, and diagnosis remains challenging because conventional tests may not reliably distinguish true clinical allergy from sensitization or cross-reactivity. Oral food challenge (OFC) remains the reference standard, but it is time-consuming, resource-intensive, and may trigger significant allergic reactions.

This interventional diagnostic study will enroll children with suspected IgE-mediated shrimp allergy. Participants will undergo OFC according to the study protocol, together with skin prick testing and blood sampling for measurement of specific IgE to recombinant tropomyosin and hemocyanin. To standardize the diagnostic procedure, OFC will be performed using black tiger shrimp (Penaeus monodon) in all participants. Additional OFCs using other shrimp species may be performed when the clinical history suggests reactions to a different shrimp species. OFC results will be used to classify participants as shrimp allergic or shrimp tolerant.

The study will estimate the proportion of true shrimp allergy among children with suspected shrimp allergy and evaluate the diagnostic performance of recombinant tropomyosin- and hemocyanin-specific IgE, alone and in combination with clinical history and skin prick test results. The findings are expected to support more accurate molecular diagnosis of shrimp allergy in children and help optimize the indication for OFC in clinical practice in Vietnam.

Inclusion Criteria:

• Children aged 1 to 16 years.
• Evaluated at the Allergy Unit of Children's Hospital 1.
• Clinical history suggestive of IgE-mediated shrimp allergy based on EAACI 2023 criteria, including at least 1 typical allergic symptom (urticaria, angioedema, vomiting, abdominal pain, diarrhea, cough, wheezing, dyspnea, or hypotension), symptom onset within 2 hours after shrimp ingestion, and recurrence on at least 2 separate exposures.
• Parent or legal guardian able to provide written informed consent; child assent obtained when appropriate.

Exclusion Criteria:

• Acute illness at the time of enrollment or challenge, including acute respiratory infection, acute gastrointestinal infection, or acute asthma exacerbation.
• Severe chronic disease, including malignancy, severe liver or kidney disease, primary immunodeficiency, or significant heart disease affecting hemodynamic status.
• Mental or behavioral disorder that prevents completion of study procedures.
• Use of immunosuppressive medication (oral corticosteroids, cytotoxic drugs, or biologic agents) within 4 weeks before enrollment, or intravenous immunoglobulin within the previous 3 months.

Exclusion Criteria:

• Acute illness at the time of enrollment or challenge, including acute respiratory infection, acute gastrointestinal infection, or acute asthma exacerbation; participants may be rescheduled after recovery.
• Severe chronic disease, including malignancy, severe liver or kidney disease, primary immunodeficiency, or significant heart disease affecting hemodynamic status.
• Mental or behavioral disorder that prevents completion of study procedures.
• Use of immunosuppressive medication (oral corticosteroids, cytotoxic drugs, or biologic agents) within 4 weeks before enrollment, or intravenous immunoglobulin within the previous 3 months.

No masking is used for study assignment. However, laboratory personnel performing recombinant tropomyosin- and hemocyanin-specific IgE measurements are independent of the clinical team and are blinded to participants' oral food challenge results at the time of laboratory assessment.