FASC: Fish Allergy in Spanish Children - A Study of New Cases of Fish Allergy in Children and Adolescents

Fish allergy is one of the leading causes of food-induced allergic reactions in children, but the clinical presentation and patterns of sensitization vary considerably among patients and geographical regions. This prospective multicenter observational study aims to characterize children and adolescents with newly diagnosed IgE-mediated fish allergy in Spain. Clinical information, diagnostic test results, and molecular sensitization profiles will be collected using standardized procedures across participating centers. Molecular allergy assessment will include component-resolved diagnostics to evaluate sensitization to major fish allergens and other relevant allergenic protein families. The study will also assess disease severity, quality of life, and regional differences in sensitization patterns. The results are expected to improve the understanding of pediatric fish allergy in Spain and contribute to more accurate diagnosis, risk assessment, and personalized management of affected patients.

Inclusion Criteria: * Children and adolescents aged 0 to 17 years (up to 18 years of age). * First clinical episode compatible with IgE-mediated fish allergy. * Evidence of allergic sensitization demonstrated by at least one of the following: * Positive skin prick test (wheal diameter ≥3 mm compared with the negative control); or * Serum specific IgE ≥0.35 kUA/L to at least one fish species or fish allergen component. * Written informed consent obtained from the parent(s) or legal guardian(s), and assent from participants aged 12 years or older, when applicable. Exclusion Criteria: * Age ≥18 years. * Non-IgE-mediated fish allergy (e.g., fish-induced FPIES). * Severe dermographism, chronic urticaria, or severe atopic dermatitis preventing reliable interpretation of skin prick testing. * Inability to complete the diagnostic procedures required by the study. * Absence of informed consent or, when applicable, participant assent.